**Silicon Vertex Upgrade for PHENIX**

March 2003

V. Ciancolo, A. Drees, H. Enyo, Y. Goto, N. Grau, J. Haggerty, J.
Heuser, J. Hill, G. Kunde, J. Lajoie, D. Lee, P. McGaughey, C.A.
Ogilvie, H. Ohnishi, H. Pei, J. Rak, K. Read, V. Rykov, N. Saito, K.
Tanida, M. Togawa, G. Tuttle, H. Van Hecke, S. White, C. Woody

![](media/image1.png){width="4.0055555555555555in"
height="3.0055555555555555in"}

[1. Introduction 3](#introduction)

[2. Goals of the Silicon Vertex Upgrade
4](#goals-of-the-silicon-vertex-upgrade)

[2.1 Spin Structure of Nucleon 4](#spin-structure-of-nucleon)

[2.2 Exploration of the nucleon structure in nuclei
6](#exploration-of-the-nucleon-structure-in-nuclei)

[2.3 Probes of Early, Highest Energy-Density Stage of Heavy-ion
Reactions
6](#probes-of-early-highest-energy-density-stage-of-heavy-ion-reactions)

[2.3.1 Energy-loss of heavy-quarks 7](#energy-loss-of-heavy-quarks)

[2.3.2 Open Charm and Beauty Enhancement
7](#open-charm-and-beauty-enhancement)

[2.3.3 J/ψ Suppression 7](#jψ-suppression)

[2.3.4 Other Physics Topics 7](#other-physics-topics)

[3 Simulations and Required Performance
8](#simulations-and-required-performance)

[3.1 Open Charm Measurement 9](#open-charm-measurement)

[3.2 Open Beauty Measurements 12](#open-beauty-measurements)

[3.3 Trigger Plans 14](#trigger-plans)

[3.4 Event Rates 15](#event-rates)

[3.5 Matching to Spectrometers 15](#matching-to-spectrometers)

[3.6 Integration with Phenix 15](#integration-with-phenix)

[4 Technical aspects of the Proposed Vertex Detector
16](#technical-aspects-of-the-proposed-vertex-detector)

[4.1 Hybrid Pixels, First Barrel Layer
16](#hybrid-pixels-first-barrel-layer)

[4.2 Silicon strips 18](#silicon-strips)

[4.3 Endcap Hybrid Pixels 20](#endcap-hybrid-pixels)

[4.4 Channel Count 20](#channel-count)

[4.5 Mechanical structure and Cooling
20](#mechanical-structure-and-cooling)

[5 Schedule and Responsibilities 22](#schedule-and-responsibilities)

[6 Budget 24](#budget)

## Introduction

This Letter-of-Intent outlines our plans to propose and construct a
silicon vertex detector for PHENIX. We outline the physics case, specify
the requirements, list possible technical options, and define the needed
R\\&D. There are three broad areas of new physics that are made possible
by the proposed Si vertex detector.

-   a large increase in the range of x over which we can extract the
    gluon spin structure function in protons with measurements of open
    charm and beauty in polarized p+p reactions

-   robust measurements of the shadowing of the gluon structure function
    in nuclei with measurements of open charm and beauty in p+A
    reactions

-   probing the early, highest energy-density phase of the matter formed
    in a heavy-ion reaction using the production of heavy flavor. There
    are several opportunities.

    -   measuring the high-pt spectra of open charm and beauty above 4
        GeV/c. The energy-loss of high-pt heavy-quarks is predicted to
        be less than for lighter-quarks.

    -   measuring the yields of both open-charm and beauty in multiple
        channels to firmly establish whether heavy-quarks are enhanced
        in the pre-equilibrium phase

    -   using the open charm yield to form the ratio J/ψ/(open charm)
        and hence to quantify the suppression of J/ ψ

    -   yield of upsilon states

Our physics goals require that we measure charm and beauty mesons over a
broad range of rapidity and transverse momentum. The proposed vertex
detector achieves this by measuring displaced tracks that are matched to
the central and muon arms of PHENIX. The broad pt, y range is achieved
by using different decay channels to reach different parts of phase
space.

The planned upgrade will operate well at 40x design luminosity and many
of the measurements need the higher luminosity, e.g. upsilon, open
beauty.

The proposed detector (VTX) is shown schematically in Figure 1, where
there are two distinct parts, central barrel and two endcaps. The barrel
consists of four concentric layers, the first populated by Si pixel
sensors, the outer three by Si strip detectors. The barrel covers -1.2
\< η \< 1.2 and almost 2π in azimuth and provides a single-track DCA
resolution of \~ 50 μm at the vertex. The forward silicon detectors are
designed to provide coverage in the angular acceptance of the forward
Muon Arms. The forward silicon cover 1.2 \< \|∆η\| \<2.7 and the almost
full azimuth angle with a resolution of \~150 μm. Each endcap comprises
four octagonal "lampshades" populated with Si pixel detectors..

![](media/image2.jpeg){width="4.331944444444445in" height="2.26875in"}

Figure 1. Cross-section view of the proposed vertex detector.

A schematic mechanical drawing developed by Hytec engineering is shown
in Figure 2.

![](media/image1.png){width="3.3694444444444445in"
height="2.5208333333333335in"}

Figure 2 A schematic cut-away mechanical drawing of the proposed vertex
detector (from Hytec).

The proposed detector complements the existing central and muon arm
detectors and these baseline detectors are essential for the proposed
physics program. Because of the different requirements to augment
central tracking and muon VTX naturally separates into two projects. The
barrel layers use largely existing technology and are in part funded by
RIKEN. The endcaps require more R&D as described in Section 4. Hence the
current plan is to stage the implementation of the VTX, first the barrel
then the endcaps.

In Section 2 we provide more details on the main physics goals of the
planned detector upgrade and in Section 3 we discuss the simulated
performance of the detector. The specific detector components and R&D
needs are discussed in Section 4, in Section 5 we discuss the schedule
and institution responsibilities, and we close in Section 6 with
construction costs.

## Goals of the Silicon Vertex Upgrade

### 2.1 Spin Structure of Nucleon

The measured quark spin-structure function in the proton integrates to
less than the required spin-1/2, a result that is described as the
\"spin-crisis"[^1]. One leading possibility is that gluons carry the
missing spin and as such PHENIX has a major goal of measuring the gluon
spin-structure function in protons. PHENIX has existing capability shown
in Figure 3 as blue lines. The different channels include direct-photons
approximately back-to-back with a high-pt hadron, charm and beauty
production. However there are significant gaps in this x-range that will
make it difficult to fully address the spin-crisis. The proposed Si
vertex detector extends the coverage to 0.004\<x\<0.3 as well as
providing significant regions where multiple channels overlap. This
overlap will provide vital cross-checks that will improve the
reliability of global fits to the spin structure function.

![](media/image3.png){width="3.5944444444444446in" height="2.725in"}

Figure 3 Expected x-range for different channels over which PHENIX will
be able to extract the gluon spin structure function. The blue bars
indicate PHENIX's existing capability while the red bars indicate the
additional coverage provided by the proposed vertex upgrade.

The vertex detector provides the following improvements in x-range

-   cc production via gluon fusion. The lower x-range is extended by
    identifying low pt (pt \>0.5 GeV) electrons as coming from displaced
    vertices from charm decay. The upgrade extends the upper x-range
    using D-\>Kπ decay channel for high-pt D's. The existing range in x
    for charm is made much more robust by the addition of a detached
    vertex signature

-   bb production via gluon fusion. With the upgrade we can identify
    displaced J/ψ from B-\>J/ψ decay which provides coverage in x
    between 0.005-0.01 and 0.1-0.2. The selection of semi-leptonic
    decays bb-\> eμX at high momentum is clean using displaced
    vertices. This extends the x_gluon coverage for these semi-leptonic
    decays to 0.02-0.3.

-   direct photon: The vertex detector provides the angle of the jet in
    coincidence with the direct photon. This constrains the x of the
    gluon by reconstructing its kinematics and permits lowering the
    range of p_T of the photon down to pt \> 5GeV. This extends the x
    coverage to 0.05 - 0.3

A third class of distributions, transversity δq(x) is needed for a
complete description of nucleon structure at leading twist. Transversity
distributions are experimentally unknown and offer a new window on
nucleon spin structure with distinct advantages: Transversity involves a
helicity spin flip amplitude and therefore is free of admixtures from
gluons. The first moment of transversity distributions is a tensor
charge and thus strictly a valence quark. The measurement of
transversity distributions through spin-dependent fragmentation of
hadrons requires the knowledge of the jet-axis. For example, in
Collins-Heppelman fragmentation the sensitivity to the transverse quark
spin results from the azimuthal distribution of hadrons around the
jet-axis. The present geometric acceptance (∆η \< 0.7) of the PHENIX
central arms is to small to permit a sufficient reconstruction of the
jets-axis, since jets typically extend over about one unit in pseudo
rapidity. However, a new tracking device close to the interaction region
would extend the geometric acceptance (∆η \< 2.0) and provide the
necessary reconstruction of the jet-angle. One option may be to
calculate the jet-angle from the centroid of tracks within a cone.

Before using open charm and beauty for spin asymmetry measurements we
need to test the next-to-leading-order (NLO) pQCD calculations for
heavy-quark production[^2],[^3]. Previous comparisons have emphasized
the total heavy-quark yieldError: Reference source not found in
proton-proton reactions, but more stringent tests are possible with the
pt spectra[^4]. Qualitatively, low-pt charm and beauty production are
dominated by gluon-fusion, while production at high-pt is expected to be
dominated by the hard-scattered gluon splitting into a QQ pair[^5].
Present data on charm and bottom production is scarce and of limited
statistics and there are no charm measurements at energies above ISR
energy.

### 2.2 Exploration of the nucleon structure in nuclei

Proton-nucleus collisions not only provide important key baseline
information for the study of QCD at high temperatures, they also address
the fundamental issues of the parton structure of nuclei. Since the
discovery of the EMC effect in the 1980\'s, it is clear that the parton
structure of a nucleon changes if it is bound in a nucleus[^6]. One of
the prime objectives for PHENIX is to measure the gluon and antiquark
distributions in nuclei.

In general all processes suitable to measure the spin gluon structure in
nucleons are also ideal for probing gluon distribution in nuclei. The
reach in x-range is indicated in Figure-3 superimposed on calculations
of the ratio of nuclear to nucleon gluon structure function[^7].

![](media/image4.jpeg){width="2.9216535433070865in"
height="2.819291338582677in"}

The red bars indicate the additional coverage provided by the vertex
upgrade compared to the baseline of PHENIX. The vertex upgrade provides
extends the x-range from the anti-shadowing region into the shadowing
domain which means we will be able to establish the shape of the gluon
structure function. The overall normalization will require a careful
cross-calibration between p+p and dAu running periods to monitor the
relative luminosity.

### 2.3 Probes of Early, Highest Energy-Density Stage of Heavy-ion Reactions

As RHIC moves to the second half of this decade the focus will shift
from the discovery phase to a detailed exploration of quark matter.
Charm and Bottom production are key observables for the earliest,
highest energy-density stage of Au+Au collisionss. The information that
the yield and spectra of heavy-flavor mesons will provide on the
earliest stages of a collision at RHIC is discussed in the following
sub-sections. Critical will be the broad reach in rapidity and
transverse momentum made possible by the proposed upgrade. This extends
PHENIX's existing capability of low-pt open charm.

### 2.3.1 Energy-loss of heavy-quarks

Colored high-pt partons are predicted to lose energy as they propagate
through the medium[^8]. The dominant mechanism is calculated to be
medium-induced gluon radiation[^9],[^10] with a smaller contribution
from elastic collisions with lower-energy partonsError: Reference source
not found. Heavy-quarks are predicted[^11] to lose less energy in the
plasma. because of stronger destructive interference effects.
Qualitatively the heavier quark is less deflected during gluon
Bremsstrahlung which leads to more destructive interference in a
"dead-cone" around the heavy-quark's trajectory. To explore this physics
will require measuring the pt spectra for open charm and beauty out to
several GeV/c. The most promising avenue for high monenta D's are the
hadronic decay channels, e.g. D=\> K+π since for these momenta electrons
from charm decay are dominated by electrons from B-decay.

### 2.3.2 Open Charm and Beauty Enhancement

Open charm enhancement has been predicted in the earliest stages of A+A
reactions[^12]^,^[^13]^,^[^14]. Heavy-quarks are produced in the initial
parton-parton collisions that occur during a heavy-ion reaction and
possibly also via gluon fusion in the pre-equilibrium stage of the
reaction. This is the mechanism originally proposed for strangeness
enhancement, but may be more powerful in the case of charm since the
rate of heavy-quark production is expected to be negligible later in the
reaction when the energy density has decreased. This enhancement is
predicted to be stronger at the LHC.

PHENIX has extracted the cross-section for open charm in the momentum
range pt\<2 GeV/c via inclusive electron spectra[^15]. However this
result required a large subtraction of background electrons from other
sources, and at moderate to high-pt the spectrum receives contributions
from both open charm and beauty. The proposed upgrade separates charm
and bottom production with high accuracy. Charm may contain a thermal
contribution while bottom could serve as a reference since open beauty
should be less affected by pre-equilibrium production.

### 2.3.3 J/ψ Suppression

The suppression of J/ ψ has been a long sought after signature of the
plasma[^16]. J/ ψ that would form from cc pairs are either screened by
the plasma or are broken up by interactions with semi-hard gluons. To
quantitatively understand suppression requires knowledge of the initial
production of cc pairs. The effectiveness of a deconfined medium in
preventing the formation of J/ ψ can be quantified using the ratio
J/ ψ/(open charm).

### 2.3.4 Other Physics Topics

The Si vertex upgrade will help other physics programs in PHENIX.
Simulations of these topics have not yet been done to quantify the level
of improvement. The upgrade will

#### narrow the mass-resolution for di-muon and di-electron invariant mass, opening up the possibility of upsilon spectroscopy. The mass resolution for reconstructing the ϒ via the ϒ→e^+^e^−^ decay is estimated to improve to \~60 MeV/c, which will enable PHENIX to separate the 1S, 2S, and 3S exited states of the ϒ, (provided there is sufficient luminosity). 

#### The J/ψ resolution in the muon arms will be improved using a vertex detector, from \~130 MeV down to \~100 MeV. This is important for separating the ψ' from the J/ψ- much of the physics is cleaner to interpret for the  ψ' since it does not have such a large contribution from feeddown like the J/ψ does.

#### provide an estimate of the contribution of charm to the e+e- continuum. This will be necessary in the search for thermal production of e+e- pairs.

#### improve high-pt tracking in the central arm by providing confirming hits close to the collision point. This will reduce background contributions to the high-pt track sample.

#### increase the signal to background for all muon-pair combinations in the muon arms by removing muons from long-lived pion and kaon decay. 

#### measure multi-strange baryons.

## Simulations and Required Performance

The performance requirements for the detector are

-   ability to match tracks from central arm and muon arm to hits in
    multiple layers of the Si detector.

    -   sufficient position accuracy so that the displacement resolution
        of the track with respect to the collision point is less than
        the cτ of charm and beauty decays, i.e. a resolution less than
        100μm, preferably at the level of 30-50 μm.

    -   for tracks at mid-rapidity the resolution needs to be
        predominantly in the rφ direction, for tracks at
        forward/backward rapidity good resolution in both rφ and z are
        required

A variety of simulations and first principle calculations have shown
that the displacement resolution is dominated by the position accuracy
of the two inner Si layers and by the amount of multiple-scattering
between the collision point and these two position measurements. A first
order guide of how well the measurement of two positions can be
extrapolated back to the collision point is

$$\sigma^{2_{\text{DCA}}} \approx \frac{\left( {\Delta x}_{1^{2}} + {\Delta x}_{2^{2}} \right)}{\text{separation}^{2}}r^{2} + \theta_{\text{ms}^{2}}r^{2} + {\Delta x}_{1^{2}}$$

where ∆x~1~ and ∆x~2~ are the two position measurements from the inner
two Si layers, r is the distance from the collision point to the first
layer, separation is the separation between the first two layers, and
θ~ms~ is the multiple-scattering angle due to material in the beam-pipe
and first-layer of Si. The first two terms approximate how well the
direction of the track can be extrapolated to the collision point while
the last term estimates the additional uncertainty in locating the
position of the track. This equation is meant as a guide only and is
superceded by simulations.

To minimize the DCA resolution, the first layer should be as close to
the collision point as is practical (small r), and the first layer plus
beam-pipe should be as thin as possible. It should be noted that over a
broad range of momentum multiple-scattering dominates (2^nd^ term above)
and that the accuracy of the hit measurement is not the determining
factor (1^st^ and third terms).

After exploring different configurations we decided on a semi-realistic
layout with reasonable thickness and positions for its Si layers
(figures 1 and 2). We plan to iterate on the design, bringing in
necessary details of the mechanics, layout, cooling, cabling etc.. The
detector has four concentric barrels of silicon which occupy the central
30 cm along the beam axis. The outer three barrel layers are Si strip
detectors placed nominally at r=10cm (barrel 4) r=8cm (barrel 3) and r=6
cm (barrel 2). The inner barrel of silicon at r=2.5 cm is composed of
pixel detectors (barrel 1). The beam-pipe is at r=2.0cm and is 500μm Be.
The endcaps comprise of four lampshade shaped disks of pixel detectors.
The inner radius for each disk is at 3.5cm

For the simulations we have used two nominal thickness for each layer: 1
and 2% radiation length. This is includes detector, readout and cooling
in a simplified one-volume effective layer. From a survey of built
detectors a radiation length of 1.5% should be achievable while 1% is
very aggressive. We are striving to minimized this thickness, in
particular for the critical first layer.

The pixel detectors for the inner barrel layer are planned to have a
segmentation of 50μm by 425μm while the endcaps have a larger footprint
of 50μm by 2000μm. The strip detectors (outer 3 layers) have a 80μm
pitch and a strip length that is 3cm long. As described more fully in
Section 4.2, the sensor has two readout strips (x and u) which provides
localization to 80μm by 800μm. This is not much larger than a Si pixel
but requires a low occupancy environment to make the projective geometry
work.

In order to maintain the occupancy below 10% in central Au-Au
collisions, the area of the sensitive elements in barrel layer 2 should
be smaller than 2.9 mm^2^. This is met by the candidate strip detectors
that have a 80μm pitch, 3cm length for a surface area of 2.4mm^2^. The
occupancy is lower in the outer two barrel layers.

In the following sections, we describe the simulated performance of the
proposed silicon vertex detector consisting of a central barrel region
matched to the PHENIX central arms and two endcaps matched to the PHENIX
muon arms. The simulations have been run within PHENIX\'s implementation
of GEANT, PISA. For convenience, we have separated each of the next
sections into measurements possible with the central PHENIX arms plus
the silicon barrel and those possible with the silicon endcaps and
PHENIX muon arms. However, there are some measurements listed below that
require all of PHENIX\'s capabilities used in unison.

### 3.1 Open Charm Measurement

**Barrel: D=\>e+X, D =\> K+π**

Open charm spectra and yields are key for the physics goals of spin
gluon structure physics, structure function work in pA reactions, and as
probes of the early stages of heavy-ion collisions. For the latter the
goal is to confirm that the excess of electrons observedError: Reference
source not found does indeed come from charm decay, and to then extend
the reach in pt to measure the energy-loss of open charm at high pt.

![](media/image5.png){width="3.8188976377952755in"
height="2.430708661417323in"}The four layers of the central silicon
barrel provide an accurate measurement of the trajectory and impact
parameter of tracks near mid-rapidity. Single electrons at different
momenta were simulated through the strawman vertex detector. This
simulation was run at zero-field and the hits from the electrons tracked
back to calculate the transverse distance-of-closest approach (DCA) to
the known point-of-origin.

For all cases the DCA resolution is better than or comparable to the cτ 
of charm and beauty decays. The power of this resolution is seen by
comparing the distribution of DCA from charm, beauty and Dalitz decays
of π^0^ in figure 5. The spectra were generated from p+p events (PYTHIA)
passed through PISA.

In the bottom panels of figure 5 are the DCA distributions for electrons
above 1 GeV/c. A DCA cut of 200 μm removes the majority of Dalitz
contribution from the electron yield. Note this is the momentum of the
electron and given the large Q-value of the D-decay, these electrons
predominantly come from low-momentum D's. Since beauty decays have
longer lifetimes, the electrons from B decays dominate at large DCA
values. By fitting the full DCA distribution with the expected shapes
from the different ct we should be able to simultaneously extract charm
and beauty yields.

This process is more difficult at electron momenta closer to 500 MeV/c
but even at this momenta charm dominates the DCA distribution above 200
μm for Si thicknesses between 1 and 1.5% radiation length.

![](media/image6.jpeg){width="5.992361111111111in"
height="5.686111111111111in"}

At higher pt we will measure charm spectra via hadronic decay channels.
For these momenta electrons from B-decay dominate the charm yield (see
section 3.3). As an illustration of hadronic decay we plot the three
body invariant mass distribution for D=\>Kππ in Figure 6. This
simulation is for p+p from Pythia events embedded in a HIJING Au+Au
background event. Simultaneous cuts (find values) are placed on three
displaced tracks and in addition the parent D must point close to the
collision vertex. These cuts produce a reasonable signal/background. The
challenge will be the low rates at high-pt. As an estimate if we assume
Au+Au 4\*blue-book luminosity, 50 full days/year, yield Au+Au=
AA\*(yield p+p) then the D=\>Kπ above pt \>4 GeV/c will produce into the
PHENIX acceptance 30kevents/year in p+p running and 10k events/year in
Au+Au. This estimate is very preliminary and requires more study regards
TOF and ![](media/image7.jpeg){width="4.081889763779528in"
height="2.2992125984251968in"}aerogel acceptance. Triggering on these
events is discussed in section 3.x.

> **Endcaps: D=\>μ+X, DD=\>μ+e+X, DD=\>μ^+^ +μ^-^ +X**

Each silicon endcap detector has four layers of pixel detectors which
measure the trajectory of particles within the nominal rapidity
acceptance of the muon arms. The impact parameter of each track is
determined accurately along the Z (beam) direction. For each detected
muon, the impact parameter is used to eliminate muons that come from
pion and kaon decays. These long-lived decays are the primary source of
background muons.

Contrasted with these background muons are \"prompt\" single muons,
which come from more short-lived decays, e.g. open charm and beauty. For
transverse momenta below \~5GeV/c the prompt muons are primarily from
semi-leptonic charm decay. Other processes which produce prompt muons,
such as J/ψ or Drell-Yan decays to muon pairs, have much smaller
cross-sections times branching ratios. Muons from B decays become
important only at larger transverse momenta.

The PYTHIA event generator was used to simulate semi-leptonic charm
decays to muons. The total charm pair cross-section was set at 350
microbarns, which is consistent with recent NLO theoretical calculations
and with the published PHENIX measurement at a somewhat lower energy.
The decay muons were tracked through the proposed silicon vertex
detector and then through the muon spectrometer using PISA.

The mean decay vertex of the detected muons is 785 μm from the
interaction vertex. This is \~2.5 times larger than the proper decay
length of semi-leptonic charm decays (318 μm), due to the lorentz boost.
The impact parameter resolution for these muons ranges from 92 to 115 μm
(check), depending on how many total layers of silicon are transversed.
By requiring that the muon vertex is within 1cm of the collision point
we remove many of the muons from pion and kaon decay while retaining
prompt muons from charm and beauty.

The pt distribution of muons that decay within 1cm of the collision
vertex shown in Figure 7. This cut reduces the muon background from
light mesons to one order of magnitude smaller than muons from charm.
Note that the removal of the muon background from pion and kaon decays
could be achieved with a detector with less spatial resolution. The
resolution requirement is driven by the physics program of measuring
open beauty (see next section).

![](media/image8.wmf){width="2.645138888888889in"
height="2.645138888888889in"}

To calculate the rate of collecting charm data we assume a 350 microbarn
cross-section, average p-p luminosity of 8 x 10^31^, 48 days of beam,
acceptance time branching ratio of 5.6 x 10^-5^ and two muon arms, about
1.4 x 10^7^ semileptonic charm decays would be recorded. This rate of
\~300,000 per day is before application of a vertex or impact parameter
cut.

Since charm is produced in pairs, coincidence measurements of
opposite-sign lepton pairs may serve to further enhance the signal to
noise in pp and pA reactions. One could use vertex identified
muon-electron coincidences to obtain a clean charm pair signal in the
rapidity interval midway between the PHENIX central and muon arms.

### 3.2 Open Beauty Measurements

B meson production, while much rarer than D production, is somewhat
simpler to measure. The challenge is the relatively low rate. There seem
to be at least two possibilities;

-   Since beauty mesons have a larger lifetime than charm mesons, it is
    possible to extract the beauty yield from the distribution of decay
    distances. At large transverse momentum beauty decays dominate the
    DCA distribution.

-   The decay channel B =\> J/ψ produces J/ψ that are displaced from the
    collision that can be used to extract the B-yield

##### **Barrel: B=\>e+X**

For momenta greater than 3 to 4 GeV/c electrons with displaced vertexes
are dominated by beauty decays. This is clearly seen in figure 8. By
placing a DCA cut on the order of 150μm we should be able to cleanly
separate electrons from beauty from all other sources. Note that at
these momenta it will not be possible to extract a charm source using
electron decay. As discussed in the previous section this will be done
via the hadronic decays of charm.

![](media/image9.jpeg){width="5.993055555555555in"
height="6.127083333333333in"}

For the rate calculation we assume Au+Au 4´blue-book luminosity, 50 full
days/year, yield Au+Au= AA\*(yield p+p). With these assumptions the
decays B=\>e+x with electron pt \>4 GeV/c will produce 320k events/year
in p+p running and 125k events/year in Au+Au.

Beauty decays are also accessible through the semi-leptonic decay
channel to muons. Since the muon arms have a relatively large acceptance
compared with the central arms, sufficient statistics can be achieved
with blue book luminosity.

**Endcaps: B =\> J/ψ=\>μ^+^+μ^−^ **

Applying a vertex cut on each reconstructed J/ψ has been used
successfully to identify B-production in experiments at lower
energies[^17]. Since the B cross-section is larger at RHIC energies, the
measurement should be easier. As the average p_T of J/ψ from beauty
decays is much larger than for prompt J/ψ, a p_T cut could also be used
to enrich the beauty sample.

Pythia was used to simulate B =\> J/ψ=\>μ^+^+μ^−^  decays. The resulting
muons are tracked through the silicon and muon spectrometers using PISA.
The muons have an impact resolution of \~55μm, significantly better than
muons from D decays, due to their larger average momentum. The pair
vertex resolution is \~133μm, while the mean decay length is \~1.1mm.
With a downstream pair vertex cut of 1mm, 39% of the B decays are
retained, while the prompt J/ψ are attenuated by a factor of 2x10^-4^.
Figure 9 shows the reconstructed Z-vertex distribution for the J/ψ from
B decays as well as prompt J/ψ.

![](media/image10.wmf){width="3.120138888888889in"
height="3.0340277777777778in"}

We have assumed a B cross-section of 2 microbarns and 3 microbarns for
J/ψ production. The branching ratio of 1.2% for B=\>J/ψ has been
previously measured. The total acceptance for these events using both
muon arms is \~11%. The rate is calculated by assuming a 2 microbarn
cross-section, average p-p luminosity of 8x10^31^, 48 days of beam,
acceptance time branching ratio of 7.8x10^-5^ and two muon arms. With
these assumptions, about 50,000 beauty decays would be recorded. This
rate of \~1,000 per day is before application of a vertex cut. With a
realistic vertex cut of 1mm, 400 events per day could be reconstructed.
Even with a factor of 10 lower average luminosity, an excellent beauty
measurement is possible.

### 3.3 Trigger Plans

We plan to use the lvl1 single electron, single and di-muon triggers as
the main physics trigger for the vtx. Higher level triggers could be a
lvl2 displaced track trigger, possibly similar to the trigger used by
CDF. CDF has implemented the trigger in hardware so is optimized for
speed. For PHENIX this could be ported to lvl2.

The CDF algorithm functions in three steps (translated into PHENIX
language); 1) outer tracks are found from either drift chambers and/or
PCs. This provides a beginning pt's and phi for each track. These tracks
are then propagated to the vtx detector. A template matching algorithm
is used to associate hits with the seed tracks. Valid patterns of super-
hits are pre-stored in a lookup table and these patterns are compared
with all the hits from the vtx. A super hit is a collection of hits the
size of which is a compromise between speed and accuracy. Patterns that
match with super-hits are also checked to see if there is a seed track
that matches to the pattern.

The original hits that contribute to the matched pattern are then passed
to a fast, linear fitting algorithm that provides the dca, pt, and phi
of the track. In CDF this algorithm is implemented in hardware and works
within 20 microseconds. The rejection factor reported by CDF for
displaced tracks is over 200. An ongoing R&D program is to explore the
feasibility of such an algorithm for PHENIX in full Au+Au collisions and
to establish an estimate of the rejection factors.

The aerogel lvl1 trigger is a candidate trigger for the channel D=\>K+π,
pt\>4GeV/c. This trigger is part of the proposed aerogel upgrade and
would fire on pions \> 2 GeV/c. These events would then be passed to the
lvl2 triggers of displaced vertexes and/or high-momentum tracks.

###  3.4 Event Rates

The event rates in the previous sections are summarized below. They
assume average p-p luminosity of 8x10^31^, Au+Au 4´blue-book luminosity,
50 full days/year, yield Au+Au= AA\*(yield p+p). All observables would
benefit from the increased luminosity in the RHICII proposal.
Difficulties in triggering the D=\>K+π, pt\>4GeV/c channel may reduce
the collected counts by up to a factor of ten.

  ------------------------ ---------------------- -----------------------
  Observable               Counts per RHIC pp Run Counts per RHIC Au+Au
                                                  Run

  D=\>K+π, pt\>4GeV/c      30k                    10k

  D=\>μ+X                  1.4 x 10^7^            0.4 x 10^7^

  B=\>e+x                  320k                   125k

  B =\> J/ψ=\>μ^+^+μ^−^    20k                    6K
  ------------------------ ---------------------- -----------------------

### 3.5 Matching to Spectrometers 

Track matching between the endcaps and the muon system spectrometers was
studied by using hijing Au-Au central collisions in a PISA simulation. A
muon track was embedded in a hijing event. The muon track was found in
station 1 from the muon tracker by demanding that the muon reached the
middle of the MUID, i.e. muon energy was \> 2.5 GeV. The distribution of
the muon hits in station 1 was was found to be +- 2 cm due to multiple
scattering in the central magnet steel. We than projected all tracks in
the central region to station 1 and found that on average 3 tracks
projected into the vicinity of the muon track. Each of these three
tracks came from the primary vertex and the displaced muon track was
easily identified with a vertex cut of 1mm.

### 3.6 Integration with Phenix

The proposed vertex detector matches and extends the capability of the
existing spectrometer arms. In addition a joint HBD/TPC is being
proposed to sit outside the vtx. The Detector Advisory Committee
recommended studies exploring the impact of the VTX on the HBD/TPC with
the possibility of standalone running for either detector. These studies
are in progress and our workplan is outlined here.

Tracking from the VTX should help the TPC and hence may Dalitz
rejection. However the VTX is a background source of electrons to the
proposed HBD detector. We are investigating how to remove many of these
electrons via analysis cuts

-   veto conversions should be removable from the outer three layers of
    the vertex detector since tracks from conversions will not have hits
    in the inner layers.

```{=html}
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```
-   the remaining conversion pairs from the first layer might be removed
    if the tracks intersect at the first layer. Since the occupancy of
    the first layer is \<1% this should effectively remove conversions
    from the inner layer as well.

```{=html}
<!-- -->
```
-   we may be able to reject conversions in the beam-pipe by removing
    electron pairs if the tracks intersect at the beam-pipe.

## Technical aspects of the Proposed Vertex Detector

### 4.1 Hybrid Pixels, First Barrel Layer

Hybrid active pixel detectors have been developed at CERN and FERMILAB
since the late 1980s, for their application in experiments at the Large
Hadron Collider (LHC)[^18]. Along this path, a series of pixel readout
chips of increasing complexity and performance was designed. Several
intermediate applications in heavy ion and high energy physics
experiments were realized. Experience with pixel detector systems was
gained in tracking stations in the fixed target experiments WA97 and
NA57. The first application of hybrid pixel detectors in a collider
experiment, pioneered by the DELPHI collaboration at LEP for its Very
Forward Tracker, operated from 1995 until the end of LEP in 2000.

**4.1.1 Readout Chip**

PHENIX will use the ALICE1 readout chip[^19] developed by the CERN EP
microelectronics Group. This chip will be used in the Inner Tracking
System of the ALICE experiment[^20] and PHENIX has the opportunity to
participate in one of the production runs. It is also the building block
of the silicon pixel telescope of the NA60 experiment at the SPS. With
an agreement between the ALICE and RIKEN readout chips and sensors are
provided to RIKEN in a common production effort.

The ALICE1LHCb pixel readout chip is currently being fabricated in a
commercial 0.25μm CMOS process. Its analog and digital circuitry
operates with a 1.6V power supply. The total static power consumption
per chip is about 500mW. This active area of the chip of 13.60mmx12.80mm
is divided into 8192 pixel cells of 50μmx425μm area that are arranged in
32 columns by 256 rows. Every pixel cell itself is divided into an
analog and a digital part. The schematics of the components are shown in
Fig.x.

![](media/image11.png){width="3.698611111111111in" height="2.31875in"}

The analog front-end consists of a pre-amplifier followed by a shaper
stage with a peaking time of 25ns. A mask flip-flop allows the pixel to
be disabled. A discriminator compares the output of the shaper with a
threshold provided globally across the chip. Each pixel contains three
logic bits that can be be used to finely adjust the thresholds
individually for every pixel to provide pixel-to-pixel threshold
uniformity over a full detector system. The outputs of the
discriminators in the pixel matrix provide a fast-OR and a
fast-multiplicity signal which is output off-chip. In every pixel, the
discriminator output is fed into the digital part of the cell. The first
stage consists of two digital delay units that store a hit for the
duration of the trigger latency. Each delay unit consists of an 8-bit
latch which, on receipt of a hit from the discriminator, latches the
bit-pattern present onto an 8-bit bus. This pattern is the Gray-encoded
contents of an up-down counter whose state changes synchronously with
the clock and has an adjustable modulo n. The result of the trigger
coincidence is loaded into the next-available cell of a 4-event FIFO,
which acts as the multi-event buffer and de-randomizer. This FIFO is
read/write addressable by means of two 4-bit busses which carry
Gray-encoded patterns. The contents of the FIFO cells waiting to be read
out are loaded into a flip-flop by the Level-2 trigger in ALICE. The
flip-flops of each column form a shift register, and the data is shifted
out using the system clock. Five latches inside each cell switch on or
off the test input to the front-end, mask or activate a pixel and
provide three bits of threshold adjustment. The latches have been
designed to be resistant to single-event upset.

Using the two delay units, each cell has the capability of
simultaneously storing two hits for the trigger latency. The 32 columns
are read out in parallel. Using a 10\~MHz clock, a complete event is
read out from the chip in 25.6 μs. The peripheral logic of the chip
contains the counters to address the delay units and the FIFOs. The
configuration of the logic and the matrix of pixel cells is performed by
means of a serial interface following the IEEE JTAG standard.

**4.1.2 Sensor/Readout Hybrid**

A pixel chip assembly is an ALICE1 pixel readout chip bump-bonded to a
pixel sensor chip. Their relative alignment is assured by the
requirement that the 20μm bonding pad of each readout pixel matches that
of the corresponding sensor pixel, for a solder bump to form between
them. The sensitive area is a 32 x 256 matrix of 50μm x 425 μm pixels in
the sensor chip, matching the dimensions of the pixel readout chip. This
active matrix of 13.60mm x 12.80mm is surrounded by a guard ring and a
scribe line, adding 560μm on all four sides. In practice, this may
slightly vary, depending on the precision of the dicing and the width of
the cut. The sensor chip\'s thickness is 300μm.

After bumping the readout to the sensor, both Si components are thinned
to a target thickness of 150 μm each. The contract with ALICE is to
provide RIKEN with enough thinned to populate the first layer of the
barrel.

> **4.1.3.Control Card**

Geometrically eight readout chips might comprise a phenix ladder. Two
ladders would then be placed to end-to-end to make one azimuthal slice
of the inner layer. Since the readout chips operate at 10 MHz, a
controller chip on the end of the ladder could address each chip in
turn, i.e. read the first 32-bit word from chip one, the first word from
chip 2 etc.. If the controller chip functions at 40 MHz then the event
is readout in 52 μs which is too long for PHENIX needs. If the
controller exceeds 80 Mhz then the readout time can be reduced to
25.6 μs.

ALICE has designed a readout card that comprises of three chips, an
analogue power supply chip, a controller chip (PILOT) and an optical
driver for the output. These chips are mounted on a thin circuit board.
To decrease the time to read an event PHENIX has two options, either a
redesign of the existing PILOT chip to move from 40 to 80 MHz or to
replace the ALICE pilot chip with a commercial, fast, radiation-hard
FPGA. The primary advantage of the FPGA would be on-ladder zero
suppression of the pixel chip readout. This would reduce the data volume
the receivers would be required to deal with. Further study will be
needed to determine which FPGA technology is most applicable to the
problem and which manufacturer provides workable solutions, as well to
address issues of power consumption, heat load, radiation hardness,
etc..

> **4.1.3.Electrical Ladder**

The technology of making connections between chips has undergone an
explosive growth in industry over the past 5 years. Our requirements of
small pitch traces, lightweight signal bus, good thermal conductivity
and low-cost for assembly are the same factors that commercial
electronics have used to drive industrial connect technology. This is
fortunate because we can ride the coat-tails of industry.

ALICE will use a multi-layered kapton cable with Al traces and and
kapton cable is being used by ALICE. Each chip requires 32 signal
traces, so for eight chips per ladder, the trace density is high
necessitating trace widths on the order of 100 microns. The wire bonds
go from the readout chip, up over the sensor to be connected to the bus.
This is shown in figure 11.

![](media/image12.png){width="4.019444444444445in"
height="2.845833333333333in"}

An alternative option for the bus is a thin ceramic (BeO) with
multi-layered signal and analogue ground and power traces. The ceramic
technology was chosen in 2002 by CDF and D0. The BeO ceramic has better
heat conductivity, smaller thermal expansion. This may make it possible
to place the bus between the readout chip and the carbon fiber support.
Such a configuration may lead to lower assembly costs.

### 4.2 Silicon strips

**4.2.1 Sensors**

The outer three barrel layers of the silicon detector will be
instrumented by silicon strips, most likely a new form of the detectors
developed and fabricated by BNL instrumentation[^21]. Tests of these
devices have started and will continue through 2003. The BNL detectors
are 3x6cm in size that are segmented as pixel detectors. The pixels are
connected by readout strips currently configured as two sets of read-out
strips placed longitudinally and diagonally. This provides simultaneous
x-u readout from a single surface. At low-occupancies this projective
geometry localizes a hit to within a pad of 80x800μm. Each strip
detector has \~1500 channels (375 channels per end, 2-readouts per end
and two ends per detector). Depending on final layout plan, the total
number of channels is 200 to 300K.

Beam tests have been carried out at KEK. An example set of position
information is shown in figure 12. The particles cross the sensors at
different channels and a clear signal is discernible above the
background.

![](media/image13.png){width="3.0708661417322833in"
height="3.1090551181102364in"}

The residual of hit position from the found track provides information
on the position resolution. This is shown in Figure 13 for one sensor.
The sigma of the residual distribution is \~40 micron for those sensors
that are 400 micron thick while the resolution is larger, \~50 micron
for thinner sensors (250 micron thick). Currently the resolution is
larger than expected and the continued improvement of the sensors is the
topic of ongoing R&D.

![](media/image14.png){width="2.7222222222222223in"
height="1.917361111111111in"}

> **4.2.2 Strip Readout**

The leading candidate for the strip readout is the SVX4 chip developed
at Fermilab[^22]. The SVX4 uses 0.25μm CMOS technology which is broadly
available. It is a 128 channel chip with a 46 deep pipeline cycled by
the beam-crossing clock. The rise time is on the order of 60 ns. A
collaboration has been established between ORNL/RIKEN and FNAL and it
may be possible to participate in a production run of these chips in the
summer of 2003

Considerable R&D is still required to integrate the svx4 into PHENIX DAQ
and to design the ladder for the strip layers. Other concerns include
the high heat load of the chip and coupling issues with the sensor. One
option is to frequently reset the svx4 since the sensor requires DC
coupling. The effects of leakage current may also be reduced if the
sensors are cooled to below room temperature.

The SVX4 chips may be loaded onto a ceramic (BeO) multi-layered board
which has good heat conductivity and low thermal expansion. Five 6cm
sensors nicely fill up 30 cm in z -- therefore natural to think of a
FEM/DCM as reading out a φ-ladder and controlling 60 readout chips per
ladder.

### 4.3 Endcap Hybrid Pixels

The endcaps are planned to be instrumented by Si pixels. It is strongly
advantageous to use the same detector technology as for the barrel
layer. Because of the greater surface area of the endcaps, we are
currently investigating whether the footprint of each pixel can be
increased to have fewer pixels per sensor and readout chip. The current
planned pixel size ( \> 2mm x 50 microns) is a compromise between
channel count (heat and cost) and occupancy. A key issue will be how
much the noise increases as the capacitance of the pixel increases.

For the readout chip one option is to use the LHCPIX1 chip as the
baseline rather than the ALICE1 chip since the LHCPIX1 chip runs at 40
MHz compared to 10 MHz for ALICE1. These two chips were developed by the
same team, have the same functionality, and the same control interface.
A similar controller card would be used for the endcaps as will be used
for the barrel pixels. Again the possibility of zero-suppression is a
strong motivation to use a FPGA in this controller card.

In addition if the chip is designed with widely spaced bumps then the
bump bonding will be easier. An attractive possibility currently under
investigation is to bump-bond both the sensors to the read-out chips and
the read-out chips to the electric bus in one assembly step. This could
dramatically reduce assembly costs but placed an increased premium on
quality control to ensure high-yield.

### 4.4 Channel Count

### 4.5 Mechanical structure and Cooling

The LANL group has initiated contact with the firm HYTEC to discuss the
conceptual design. HYTEC are the mechanical design team for the ATLAS
silicon vertex detector. For PHENIX they have designed the station 1
muon detectors and the station 2 spider and also did the finite element 
analysis of the station 3 octants. Hytec was commissioned to do a
preliminary design study, from which we quote the following from their
report[^23].

"The basic requirements for the PHENIX tracker are given in the outline
below.

1\. Clamshell Design:

i\. Separates into two halves along the vertical axis

2\. Detector Coverage:

i\. Hermeticity: single overlap circumferentially

ii\. 160^o^ coverage in each half of barrel section

iii\. 4 layers of pixels and/or strip detectors in barrel section

iv\. 180^o^ coverage in each half of the end cap sections

v\. 4 layers of pixel detectors in end cap sections

3\. +/- 40^o^ Envelop for HBD/TPC maintained around barrel section

i\. End cap pixel disks, utilities, and barrel detector end support are
outside of

envelope

ii\. Main clamshell support structure is inside of envelop, but less
than 0.5% RL

4\. Radiation length (RL) of 1% or less for each detector layer
(includes: detectors, structure, and utilities)

5\. Dimensional and structural stability of less than 25 µm for
detectors and 100 µm

gravitational structural stability of entire tracker

6\. Utility Routing:

i\. Along barrel end support for barrel region

ii\. Radial at pole tips for the end caps

7\. Mounting of Tracker:

i\. Off of magnet pole tips

ii\. Tracker to behave as a rigid body structure

iii\. Operating Temperature: Room temperature (or possibly 0^o^C
option?)

**4.5.1 Material Selection**

"The use of Graphite Fiber Reinforced Plastic (GFRP) sandwich composites
for the base structure is suggested because of the substantial gain in
the stiffness to weight ratio. Fiber selection for the GFRP was deferred
to the candidate that is most readily available and at a reasonable
cost. M55J is the most widely used standard in the composites industry,
and so it was used throughout the remainder of the structural study."

**4.5.2 Structural Analysis Summary**

"The structural analysis of several concepts revealed the following
observations. Use sandwich composites for the frame structure instead of
solid laminates or some combination of both. Radiation length
requirements can be met with GFRP sandwich composites, and sandwich
composites have been show to have better stiffness to weight ratios.
Outer frame structure should be a single diameter size across all three
detector regions and as large a diameter as possible for the given
envelope for the PHENIX Pixel Detector upgrade.

-   Stability and alignment requirements can be attained with a
    clamshell design, if sufficient R&D is done on connection issues
    regarding the two clamshell halves.

-   Suggest using an eight-sided shape for the outer structure. The
    eight-sided shape lends itself to simpler fabrication and allows for
    better routing of utilities out of the barrel region and end cap
    regions.

-   Structural end disks to close out the tracker support structure are
    recommended for preventing deformation of the structure under
    dynamic load inputs at the tracker support points."

**4.5.3 Cooling Analysis Summary**

"First order calculations were made for both regions. The results of
these preliminary analyses are:

*Coolant*

-   Use single phase coolant, as opposed to using phase change coolants;
    this is suggested as a means to significantly simplify the attendant
    coolant system

-   Use perfluorcarbon fluid, C5F12 or C6F14, with the final decision
    reserved for the final system study

-   Flow coolant under turbulent flow conditions to enhance convective
    heat transfer coefficients, thereby substantially reducing the
    temperature drop in the coolant film and the gradient in the
    detector support structures

-   Supply the coolant at 20°C inlet, unless sub-cooling of the overall
    detector is required.

*End Cap Region*

-   Use a flat conical panel sandwich structure for supporting the
    modules, with module mounting alternating front to back on adjacent
    panels. Panels are termed sectors, with cooling provided to two
    adjacent sectors in series. Series connection of adjacent sectors
    provides modularity of two. Higher modularity may weaken the
    detector reliability in the event of an isolated failure of a
    cooling component.

-   Construct the structure as a half conical structure, mounted to an
    outer clamshell sandwich structure.

-   Cooling of the End Cap sectors requires removal of nominally 15W per
    sector, at a comparatively low heat flux. A 2mm inner tube diameter
    is suggested with a mass flow rate of 9.8g/s for a pressure drop of
    6psi per sector. Resulting peak temperature in the surface of the
    sector should be on the order of 4.5°C or less. Bulk fluid
    temperature rise for two sectors would on the order of 3°C. Pressure
    drop can be reduced to under 1psi by using a 3mm diameter cooling
    tube.

-   The preliminary sandwich spacing used in the thermostructural
    solution was 2mm, with the void between cooling channels filled with
    carbon foam. The cooling channel is sandwiched between two thermally
    conductive facings. The facings were assumed carbon-carbon material
    for reasons of high thermal conductivity and structural stiffness
    Further studies of the end cap clamshell panels are suggested for
    refining the composite sandwich design and to assess thermal
    strains. However, the thermal strains can be minimized by using a
    stiff composite sandwich structure.

*Barrel Region*

In the Barrel Region, we chose to analyze the ladder concept for the
silicon strip layer since the total heat load per ladder is greater, 27W
versus \~8W per ladder for the pixel layer. The next step in the study
will include the pixel ladder design. Continuing the listing of findings
and suggestions:

• Use a ladder, or stave, concept supported at its ends by composite
rings.

-   One end of the ladder would emulate a simple support and the other a
    fixed end support. These boundary conditions were chosen to minimize
    thermal strains.

-   Suggested stave structure comprises a C-C thermal plane for mounting
    pixel modules, or silicon strip detectors. To add stiffness to the
    long flat surface, a thin, 0.4mm OMEGA shaped composite is bonded to
    the back of the thermal plane.

-   Cooling tube is bonded to the back of the C-C thermal plane with a
    C-C tube support, using a rigid room temperature adhesive

-   Use an Aluminum cooling tube 3mm in diameter supplied with a 23g/s
    single-phase perfluorocarbon fluid, e.g., C5F12, layer 3 or 4.
    Estimated bulk fluid temperature rise is 1.1°C for 27W per stave
    heat pick up. Corresponding pressure drop is approximately 1psi per
    stave. Estimated peak temperature for a silicon layer (3 or 4) is
    8.6°C. Analysis is required for the pixel layer; temperatures may be
    somewhat higher due to the higher localized heat flux, 0.7W/cm2
    versus 0.35W/cm2 for the silicon strip layer.

-   Preliminary estimate of bowing for the silicon strip layer, along
    its 30cm longitudinal axis, due to thermally induced strains is
    modest. This assumes the coolant is supplied at 20°C. If detector
    sub-cooling to 0° C is required, the thermally induced strain would
    increase to 80µm. This thermal component strain for a pixel layer
    stave, with its higher localized heat flux, may be greater.

"Overall, we feel the system parameters and design approach selected for
consideration by the PHENIX collaboration reflects a conservative design
with a focus on simplicity to hold R&D and acquisition costs down. The
basic structural concepts chosen for supporting the pixel modules are
expected to stay within or close to the specified radiation length
budget."

## Schedule and Responsibilities

For planning purposes the proposed vertex detector is split into two
projects: project 1 includes the four layers of the barrel and project
two includes the two endcaps. They share commone mechanical support and
infrastructure.

The draft schedule for project 1. It is planned to install the full
barrel in the summer of 2006 ready for run07. A prototype ladder may be
ready for installation in summer 2005. The funding for project 1 is
proposed to come from RIKEN and DOE.

![](media/image15.png){width="4.785416666666666in"
height="3.6993055555555556in"}

The responsibilities for different parts of project 1 are listed in the
following table.

The schedule for project 2 is shown below. It is planned to install the
endcaps in the summer of 2007 ready for run08. A prototype ladder may be
ready for installation in summer 2006. The funding for project 1 is
proposed to come from DOE.

![](media/image16.png){width="4.571527777777778in"
height="2.4145833333333333in"}

The responsibilities for different parts of project 2 are listed in the
following table.

## Budget

Below is a summary of the construction budget for project 1 and project
2

  -------------------------------------------------- --------------------
  **Construction Project 2 - EndCaps**               **DOE (k\$)**

  **Mecanical support and cooling (2 endcaps)**      **195**

  **Hybrid pixel layers (2 encaps)**                 **4766**

  **Management**                                     **100**

  **Total**                                          **5061**

  **Overhead on DOE contribution**                   **1257**

  **50% contingency**                                **2458**

  **Total**                                          **8849**
  -------------------------------------------------- --------------------

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[^11]: kharzeev dead-cone

[^12]: E. Shuryak Phys. Rep 61, 71 (1980)

[^13]: P. Levai et al, Phys. Rev C. 51, 3326 (1995)

[^14]: Z. Lin and M. Gyulassy, Phys. Rev. C. 51, 2177 (1995)

[^15]: K. Adcox et al., Phys. Rev. Lett. 88, 19203 (2002)

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[^17]: E789 Phys. Rev. Lett. 74, 3118 (1995).

[^18]: Heijne, E.H.M., Semiconductor micropattern pixel detectors: A
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[^19]: W.\~Snoeys et al., Pixel readout electronics development for the
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[^20]: The ALICE Collaboration, ALICE - Technical Design Report of the
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[^21]: http://ssd-rd.web.cern.ch/ssd-rd/rd/talks/Li-rd-2001.pdf

[^22]: svx4 reference

[^23]: HYTEC report