# Presentation: 483994

## RHIC  d-A and A-AMike Leitch, P-25

- PHENIX  Arms

**Parton structure, modification in nuclei and the Quark Gluon Plasma (QGP)**
**PHENIX: Muon arms, Multiplicity & Vertex Detector (MVD) and Forward Calorimeter (FCal)**
**Performance & Commissioning**
**LANL Contributions**
**     ****& Obligations **

- MVD

## RHIC/HENP Physics Program at LANL

***Parton structure, modification in nuclei, spin-dependence and the Quark Gluon Plasma (QGP):***
- Flavor asymmetry of the nucleon sea and its spin-dependence (M. Liu)
- Polarized structure functions from polarized p-p collisions (M. Liu)
- Gluon structure functions and their shadowing in nuclei
- Energy loss of partons in nuclei. Contrast cold-nuclear matter (d-Au collisions) with hot/high-density matter (Au-Au collisions)
- Heavy-quark production and suppression:  J/suppression in d-Au collisions and in hot/dense matter
- Reaction plane and centrality dependence for d-Au and A-A collisions, e.g. how much nuclear matter does a      pass through after it is created or what densities are achieved in a collision

## xF

**Drell-Yan**

**E866 R(W/Be)**
**E772 R(W/D)**

***Drell-Yan Process***

_**Modification of parton momentum distributions of nucleons embedded in nuclei,  e.g. shadowing – depletion of low-momentum partons.**_

- _Gluon Shadowing - Largely Unknown_
**Gluon shadowing for J/****Ψ -> μ****+****μ******** in**** PHENIX?**
*** ******Eskola et al. hep-ph/0104124*****: ~ **_**0.8**_
** *****Kopeliovich et al. hep-ph/0104256***** : ~ **_**0.4**_
** **_**Need to measure it in d-Au collisions**_

-  ***x******2****  is the momentum fraction of the target nucleon that a parton (quark or gluon) carries*
* ****x******F**** is fraction of maximum CM momentum,*
*i.e. “how fast is it (e.g. a J/****) going”*

**X****2**

**Eskola**

**Kopeliovich**

**d+Au -> J/******

**x****F**

- _Anti-quark_
- _Shadowing_

## Process Dependence of  Shadowing? 

*Kopeliovich et al*
*hep-ph/0104256*
*& hep-ph/0205151*

- without

**Shadowing much weaker for open-charm production than for charmonium **

- Anti-shadowing

- Whereas in the ordinary parton model shadowing “factorizes” and is a “property” of the nuclear structure function

_**Process Dependence of  Shadowing?**__** **_

- with shadowing

## Quark energy loss in nuclear matter

**dE/dz = -2.73 ****±**** 0.37 GeV/fm**
***Johnson, Kopeliovich et al. PRL ***_***86***_***, 4483 (2001)***

**Shadowing only**

**dE/dx & Shadowing**

_**Quark energy loss in nuclear matter**_

***E772 Drell-Yan data***

- x1

- x1

## Anomolous Suppression of high-pT Hadrons

_**Anomolous Suppression of high-p**__**T**__** Hadrons**_

-  Most significant result from RHIC so far, e.g. Wang -> _7.3 GeV/fm_ parton dE/dx
-  d-Au baseline is critical for verification

## Production of heavy vector mesons, e.g. J/Ψ, Ψ ', and the QGP

-  Hadronization time, i.e. distance before physical resonance formed
-  Absorption on nucleons or on co-moving light quarks
-  Feed-down from higher mass resonances, e.g. χc

_**Production of heavy vector mesons, e.g. J/**__**Ψ**__**, **__**Ψ ', **__****__**and the QGP**_

_**J/**__**Ψ**__** suppression – an effective signature of Quark-gluon plasma (QGP) formation?**_
-  **Color screening in a QGP would destroy       pairs before they can hadronize into charmonium**
** ****Began with prediction by Matsui and Satz (Phys. Lett. B178, 416 (1986)) that Debye color screening will lead to suppression of charmonium production in heavy ion collisions, if a quark-gluon plasma is formed.**
** ****More recent predictions of increased J/******** production at RHIC from recombination.**
** ****But ordinary nuclear effects also absorb or modify J/****Ψ’s**

***Quark-gluon Plasma (QGP) deconfined quarks in a hot-dense region, a phase transition***

## Nuclear Dependence of Charm Production: E866/NuSea

-  **J/****Ψ**** and ****Ψ****’ similar at large x****F**** where they both correspond to a      traversing the nucleus**
** ****But ****Ψ****’ absorbed more strongly than J/****Ψ****  near mid-rapidity (x****F**** ~ 0) where the resonances are beginning to be hadronized in nucleus****.**

***Phys. Rev. D52, 4251 (1995)***

## NA50 -- Anomalous J/ Suppression, Evidence for QGP??

_**NA50 -- Anomalous J/**__****__** Suppression, Evidence for QGP??**_

- Expected J/ yields are corrected for "ordinary" nuclear absorption assuming **6.4 mb **absorption cross section

**J/******** -> ******** decays measured / expected**

** ****We need a comprehensive understanding of charmonium production in nuclei as a baseline for QGP studies**

*PL B477, 28 (2000)*

## We can not discriminate between scenarios, given our present statistical accuracy

**We can not discriminate between scenarios, given our present statistical accuracy**

**Phys. Lett B 521 (2002) 195**

-  All curves        normalized to  pp data point
- (bit of a hoax)

- QM02 – Run-II Au-Au
- Data (~10 J/ events)

## Expected J/’s in present PHENIX d-Au (run-III)

- 	PHENIX has very broad coverage in xF, pT and x2 by combining
- North Arm
- Central Arm
- South Arm

| #J/ | d-Au
10 wks | p-p
3 wks |
| --- | --- | --- |
| South | 8.2k | 10.8k |
| North | 7.5k | 9.9k |
| Central | 2.1k | 2.8k |

- from PHENIX Beam Use Proposal 8/16/02

## PHENIX Muon Arms

- Acceptance : 1.2 < |**| < 2.4,  
- Muon minimum momentum ~ 2 GeV/c

- Tracking

- Stations

## South Muon Arm

- North Muon Arm

- Multiplicity & Vertex Det. (MVD)

## North Chambers and Mechanics

- Tracking chambers – designed at LANL and built with collaborators

**Station 1 Quadrant at BNL**

**Station 2 Octant at BNL**

**Station 3 Octant at BNL**

**Station 2 Support Structure**

## Front-End Electronics (FEE) Installation and Commissioning

-  Copy of South arm FEE led and built by LANL, with minor changes
-  With strong contribution from French for North arm including funding and manpower

- Electronics being assembled

- And installed

## LANL North Arm FEE Contributions

-  Mechanical support designed and overseen at LANL, built at NMSU
-  Calibration system
-  Optical Fiber<-->Copper electronics system
-  HV Distribution system designed and built at LANL
-  Rack and cable layout completed at LANL

**Optical ******** Copper Translation System**

**North Magnet Layout and FEE Support Structures**

**Calibration System**

**HV dist.**

## J/ from the 1st Year

## Tracking/pattern recognition progress led by LANL

-  Better handling of skipped planes
-  Corrections for swapped cables
-  Better projections between stations
-  Important for p-p (not just Au-Au)
-  Realistic sigma’s for points in each plane
- Mixing with real events to determine efficiencies more reliably
-  Resolved acceptance disagreements between simulations and data
-  _**Mass resolution now agrees between simulations and data: ~180 MeV for J/**__****_

_**Tracking/pattern recognition progress led by LANL**_
**(We wrote the original code and have led all developments)**

-  Mass(GeV)

*Run-II*
*p-p data*

## Radiographs of active area for South arm in run-II. (Three stations with 3 or 2 gaps each)

**Sta-1**

**Sta-2**

**Sta-3**

- Vast improvement for present (run-III) after extensive repairs to electronics and HV during shutdown

**Gap-1**

**Gap-2**

**Gap-3**

## Dimuon Event  from Run-III

## Multiplicity and Vertex Detector (MVD) 

**Beam goes through here**

- _Multiplicity and Vertex Detector (MVD) _

- ~64 cm long barrel
-  “1.5 layers” with ~25K Si strips
- ~6K Si pad detectors in endcaps
-  covers -2.5 < y < 2.5  (9 <  < 181 deg)

**1/4 MVD under construction:**

**Readout**
**electronics**

- What is it?

- Brief history:

-  Problems with Multi-chip module (MCM) yield & production schedule.
-  Phenix year-1 ~30% instrumented
-  Phenix year-2 ~60% instrumented
-  Phenix year-3 completed

## From the Review of the MVD at BNL, Oct. 29, 2002:

**“***The MVD group has made good progress in dealing with the technical problems that have plagued them in the past two runs. *_*Hardware problems have all been solved and a majority of electronics problems have been solved*_*. Construction and installation are under control with adequate manpower.”*
*“*_*The physics case for the MVD is compelling in pp, dA,*_* with no significant drawbacks. These include – giving a precision vertex for muon measurements, multiplicity measurements over a wide rapidity region, reaction plane measurements, and Dalitz rejection and track confirmation for pp measurements and centrality determination.”*

## Multiplicity & Vertex detector (MVD)

**dN/d****η**** from MVD**
**for 125 Au-Au simulated events**

**PHENIX w/o MVD : | ****η**** | < 0.35**

- simulation

-  Precision vertex (~0.1 mm)
-  Multiplicity (impact parameter)
-  reaction plane
-  fluctuations
-  dN/dfor charged particles over very broad rapidity range

## MVD-BBC vertex diff. 

_**MVD vertex resolution & efficiency for p-p,  p-Au & Au-Au collisions**_

**2 cm or better vertex resolution needed by muon tracking to preserve J/******** resolution of ~130 MeV; otherwise 200 MeV**** **

**MVD-BBC vertex diff. **
**( cm): **
**Good resol-ution**

*Simulation*

*Run-II*
*Au-Au data*

## Reaction Plane

- In a heavy ion collision, the initial collision
- zone is “almond-shaped”
- High pressure in the excited region
- translates the initial spatial asymmetry
- into a measurable asymmetry in the
- final state. The asymmetry is ~5%,
- but there are ~5K particles.
- The MVD should be able to find this reaction plane to within 10-20 degrees. This gives another interesting way to look at jet suppression and J/ suppression vs. the length of excited matter traversed.

- b = impact
- parameter
- (beam into page)

- shorter
- path

- longer
- path

## The PHENIX forward-hadron calorimeterTagging with grey protons

_**The PHENIX forward-hadron calorimeter**__**Tagging with **__***grey***__** protons**_

**Refurbished E864 calorimeters**
**installed inside ring for PHENIX**

** ****Measuring forward protons from the fragmenting nucleus in d-A collisions provides a sensitive measure of N****binary ****(# binary collisions)**
** ****Measurement of the undeflected proton from a deuteron in the d-A program can help differentiate between p-A like collisions and n-A like collisions****.**

- First result - correlation with the PHENIX beam-beam counter

## LANL Contributions to PHENIX

-  **Defined much of the physics program for PHENIX muons and spin & major contributors to PHENIX CDR**
** ****Led in getting the muon arms into PHENIX & conceived the spin program including bringing the Japanese (RIKEN) group into PHENIX.**
** ****Physics-based design & construction of Muon spectrometers & MVD in PHENIX**
_**Continuing Contributions**_**:**
** ****Finish commissioning MVD & Muon Arms (2003)**
** ****Planning for Run-III, e.g. triggering (Silvermyr)**
**Run-III: d-Au ~ Jan. 1 (11 wks); p-p ~ Apr. 7 (3 wks)**
** ****Shifts (~2 weeks/person), sub-system experts (MVD & MuTr) on call 24hrs/7 days,  7 periods as shift-leader so far, period coordinator(Leitch, 2 weeks as floor mgr.), ...**
** ****Luminosity targets are sufficient to get, e.g. ~ 15k (d-Au)  J/********’s**
** ****Detector Council representatives for MVD (Sullivan) and Muon Tracking (Leitch); PHENIX Executive Council (Leitch)**
** ****Software/Analysis lead for Muon tracking (Brooks, McGaughey, Liu) and MVD (Sullivan, vanHecke). **

## LANL Contributions to PHENIX - II

**Convenor for hadron group (Sullivan, 2-yr term)**
**Many paper writing committees, e.g. first J/******** paper (Brooks), single-electrons (Leitch), long hadron paper (Burward-Hoy, van Hecke), 1****st**** PHENIX paper (Silvermyr), ...**
** ****Former high-p****T**** convenor for STAR (Kunde)**
** ****RHIC/AGS Users Executive Committee (Burward-Hoy)**
** ****Maintenance**
** ****with strong French contribution for muon electronics**
** ****For MVD; lifetime limited by plans for silicon vertex detector (<= 2005?)**
** ****Silicon vertex upgrade design & construction (LDRD seeded, R&D funding requested); focus on conceptual/engineering & design in next year (Lee, McGaughey).**
** ****Many students have worked with us on this project**

_**LANL Contributions to PHENIX - II**_

## People in RHIC/HENP Program

- Barnes, Brooks, Kunde, Lee, Leitch, Liu, McGaughey, Moss, Sullivan, VanHecke; Silvermyr(PD), Burward-Hoy(PD); and Sondheim, Boissevain (Engineers)
-  Recently added two new high-level physics leaders (Liu, Kunde) and 1 postdoc. Plan to add at least one more postdoc.

_**Issues & Concerns**_
-  Finally emerging from construction & need to assure a strong leadership in physics. Relying on good people – e.g. new high-level staff and more postdocs are critical!
-  Working towards more visability to the community & our sponsors in terms of physics leadership
-  Advancing new physics-motivated construction projects while still maintaining a balance with strong leadership in physics