# Presentation: 656030

## Super LHC - SLHC

** ****LHC Detector Upgrade  **
**Dan Green**
**Fermilab**

## Outline

**Physics Basics**
**Z’ vs**
**Rapidity Range**
**Minbias**
**Pileup and Jets**
**Occupancy and Radiation Dose **
**Tracker Upgrade**
**Calorimetry**
**Muons**
**Trigger and DAQ**

**CERN-TH/2002-078 “Physics Potential and Experimental Challenges of the LHC Luminosity Upgrade”**
**10x will be challenging!**

## Mass “Reach” and L

**The number of Z’ detected in leptonic decays is:**
**For                                      , if N = 100 is discovery level then M ~ 5.3 TeV is ~ the mass “reach” in 1 year (M=4 -> 5.3 TeV).**
**The leptons will be sharply limited to low |y| or large angles (“barrel”).**

## Mass Reach vs L

**In general mass reach is increased by ~ 1.5 TeV for Z’, heavy SUSY squarks or gluinos or extra dimension mass scales. A ~ 20% measurement of the HHH coupling is possible for Higgs masses < 200 GeV. However, to realize these improvements we need to maintain the capabilities of the LHC detectors.**

**VLHC**
**LHC**
**Tevatron**

## Kinematics

**Heavy States decay at wide angles. For example Z’ of 1 and 5 TeV decaying into light pairs. Therefore, for these states we will concentrate on wide angle detectors.**

- 1 TeV

- 5 TeV

-    barrel                               **y**                                    barrel

## Inclusive Interactions

**The inclusive p-p interaction has an inelastic, non-diffractive cross section       ~ 50 mb.**
**It produces ~ equal numbers of                   which are distributed ~ uniform in rapidity, y, with a “density”                            ~ 9 pions per unit of y.**
**The pions have a distribution in transverse momentum with a mean,            ~ 0.6 GeV**.

## Detector Environment

**Bunch spacing reduced 2x. Interactions/crossing increased 5 x. Pileup noise increased by 2.2x if crossings are time resolvable.**

## Pileup and Luminosity

**For     ~ 50 mb, and       = 6 charged pions/unit of y with a luminosity                        **
**   ****and a crossing time of 12.5 nsec :**
**In a cone of radius = 0.5 there are ~ 70 pions, or ~ 42 GeV of transverse momentum per crossing. This makes low E****t**** jet triggering and reconstruction difficult**.

## Z’(120) at L/5 and L

**dR**

**Log(z), z = k/E****T**

- ET(GeV)

**Jet cone and 90 degrees to cone in ******

## Z’(120) Mass Resolution

**Note that the calorimeter cells are still fairly sparsely populated (granularity                                                    **
**                          ****) at 10****34**** . With the cuts shown, the dM/M with Gaussian fits is the same at L/5 and at L. Use the fact that QCD implies that there is a core of the jet at small dR and large z. Extend to 10x L using tracker and energy flow inside the jet? If x-ing is time resolvable, pileup is “only” 5x. Tracker can be used (energy flow) to remove charged energy deposits from vertices within the x-ing which are not of interest. **

- M(GeV)

## Tracker and Energy Flow

**For 120 GeV Z’ match tracks in ******** and ******** to “hadronic” clusters within the jet. Improves dijet mass resolution. Units are HCAL tower sizes. Also use track match to remove  charged pion deposits from pileup vertices ?**

- d

- d

**E****T****(GeV)**

## WW Fusion and “Tag Jets”

**These jets have**
** ****~ pileup R = 0.5 and <y> ~ 3. Lose 5x in fake rejection. We must use the energy flow inside a jet cone to further reduce the fake jets due to pileup (~ uniform in R). **

- WW fusion

**Pileup, R=0.5, |y|=3**

## Tracking Detectors

** ****Clearly, the tracker is crucial for much of the LHC physics [e.g. e, ********, jets (pileup, E flow), b tags].**
**The existing trackers will not be capable of utilizing the increased luminosity as they will be near the end of their useful life.**
**It is necessary to completely rebuild the LHC tracking detectors.**

## Tracker - Occupancy

**The occupancy, O,  for a detector of area dA and sensitive time time dt at (r,z) is**
**e.g. Si strip 10 cm x 100 ********m in a 12.5 nsec crossing at r = 20 cm is 1.5 %**
**For higher luminosity, decrease dA, or decrease dt (limit is x-ing time) or increase r – smaller, faster or further away.  **

## Tracker Occupancy

**Preserve the performance using        :**
**Push Si strips out to ~ 60 cm. – development**
**Push pixels out to 20 cm. – development**
**For r < 20 cm. Need new technologies – basic research**
**Shrink dA 5x at fixed r to preserve b tagging? If 12.5 nsec bunch x-ing, need 5x pixel size reduction.**
**Possibilities**
**3-d detectors – electrodes in bulk columns**
**Diamond (RD42) - radhard**
**Cryogenic (RD39) – fast, radhard**
**Monolithic – reduced source capacity.**

## Monolithic Pixel - DEPFET

**Combine the detector and the readout for pixels?**

## Tracker – Ionizing Dose

**The ionizing dose due to charged particles is:**
**The dose depends only on luminosity, r, and exposure time ********.**
**For example, at r = 20 cm, the dose is ~3 Mrad/yr – ignoring “loopers”, interactions, .... ******** “naïve” expectation.**

## Tracker ID vs. Radius

**     ****naive**

- 1

- 2

- 3

**Define 3 regions. With 10x increase in L, need a ~ 3x change in radius to preserve an existing technology. **

## Tracking R&D -I

**Region 1: r < 20cm**
- Occupancy -> Need pixels of a size factor ~ 5 smaller than used today
-     (125x125 m2 -> ~ 50 x ~ 50 m2) -> benefit b-tagging
**R&D**: Pixels Sensor Technologies
-  new sensor materials – defect engineered Si, CVD diamond, SiC, passivated amorphous Si etc.
- 3-D detectors and new biasing schemes
-  Cryogenic Si tracker development
-  monolithic pixel detectors
**Region 2: 20<r<60 cm**
- Need cell sizes 10 times larger than current pixels but at 10 times lower cost/channel than current Si microstrips -> benefit p-resolution and pattern recognition
- Si Macro-pixels of an area < 1mm2 : pads or shorter  strips ?
- Could be upgrades of innermost Si  strip layers of current detectors
**R&D**:  to demonstrate low-cost macro-pixels concept, thin Si detectors.

## Tracking R&D - II

**Region 3: r > 60 cm**
**Si-strips –decrease size of strips i.e. increase no. of channels by > 50%**
**Use standard ‘radiation resistant’ ******** strip technology**
**R&D: Feasibility of processing detectors on 8” or 12’ Si wafers. Monitor commercial  production progress.**
**Engineering**
**R&D: new materials, light weight, stable structures, cooling, alignment, implications for cryogenic operation, installation and maintenance aspects**
**Activation: 250 mSv/h – implications for access and maintenance**
**Cost: Reduce cost/channel by a factor of 10**
**Timescale : Need ~ 8-10 years from launch of R&D**
**	****~ 4 years to build, after  ~ 4 years of R&D and prototyping** ?

**Notes:**
Standard microstrip technology :single sided,  p+n technology, integrated AC coupling, polysilicon bias, 100 crystal orientation, standard 0.20-0.25 w/p ratio and metal overhang 

## Electronics – Moore’s Law

**Micro-electronics: line-widths decrease by a factor 2 every 5 years. DSM (0.25 ********m) is radiation hard.Today 0.13 ********m is commercially available. In the lab 0.04 ********m, e.g. extreme UV lithography, is in existence. Expect trend will continue for a decade.**
**R&D**
** ****Characterize emerging technologies**
** ****more radiation tolerance required – dose and Single Event Effects**
** ****advanced high bandwidth data link technologies**
** ****system issues addressed from the start **

**Notes:**
The current LHC experiments would not have been possible without extensive use of microelectronics technology.
Successful application result of intensive R&D programme (DRDC)

## ECAL – Shower Dose

**The dose in ECAL is ~ due to photon showers and is: **
**In the barrel, SD is ~                .  In the endcap, SD ~ **
**At r = 1.2 m, for Pb with Ec = 7.4 MeV, the dose at y=0 is 3.3 Mrad/yr, at |y|=1.5 it is 7.8 Mrad/yr.**
** **

## HCAL and ECAL Dose

**The dose ratio is ~                                           . Barrel doses are not a problem. For the endcaps a technology change may be needed for 2 < |y| < 3 for the CMS HCAL. Switch to quartz fiber as in HF?**

**     ****naive**

**ecal**
**hcal**

## ECAL

**For both ATLAS and CMS the barrel will probably tolerate the increased dose. There are issues of  ~ 2.2x increased pileup noise and poorer isolation for electrons. Shorter shaping times to resolve x-ing?**
**ATLAS LA has space charge and current draw issues. CMS has APD leakage current noise issues in the barrel. The CMS endcap needs development. **

## HCAL - CMS

**Both ATLAS and CMS will function in the barrel region.**
**In the 3<|y|<5 region, a reduction to y < 4.2 keeps the dose constant. The loss of efficiency is not terrible (peak “tag”rate at |y|=3). Or replace quartz fibers with high pressure gas? Better tower granularity might be needed due to pileup and “fake” jets.**
**At |y| ~ 3 the CMS scintillator needs development – improved scintillator or go to quartz fibers ( volume degraded is quite small).**

## HCAL - Coverage

**Reduced forward coverage to compensate for 10x L is not too damaging to “tag jet” efficiency**

## Scintillator - Dose/Damage

**This technology will not survive gracefully at |y| ~ 3. Use the technology that works at LHC up to |y|~ 5, quartz fibers?**

- |y|=2, 1 yr.

## Muons and Shielding

**There is factor ~ 5 in headroom at design L. With added shielding, dose rates can be kept constant if angular coverage goes from |y|<2.4 to |y|<2. **

- r

- r

- z

## Trigger and DAQ

**Assuming LHC initial program is successful, raise the trigger thresholds.**
**Rebuild trigger system to run at 80 MHz. Utilize those detectors which are fast enough to give a BCID within 12.5 nsec (e.g. Calorimetry, Tracking).**
**Examine algorithms to alleviate degraded e isolation, for example.**
**Design for the increased event size (pileup) with reduced L1 rate and/or data compression.**
**For DAQ track the evolution of communication technologies, e.g. 10 Gb/sec Ethernet.**

## 300 GeV Pion – H2 test Beam

**HTR  - Bunch crossing number (LHC)**

**The shape of the pulse in time is ~ as expected – due largely to scint flours. Bunch crossing ID can be extended to 12.5 nsec ( 80 MHz) as established in test beam.**

**E**

## Summary

**The LHC Physics reach will be substantially increased by higher luminosity.**
**To realize that improvement, the LHC detectors must preserve performance.**
**The trackers must be rebuilt – with new technology at r < 20 cm.**
**The calorimeters, muon systems, triggers and DAQ will need development.**
**The upgrades are likely to take ~ (6-10) years. Accelerator is ready ~ (2012, 2014). The time to start is now, and the people to do the job are those who did it for the present detectors.**

## SLHC Detector - Summary

- Tracking and b-tagging
-  Isolated high pT (> 20 GeV) tracks -  it should be possible to maintain similar efficiency and momentum resolution
-  without a tracker upgrade, for fixed b-tagging efficiency, rejection against light quarks will deteriorate by factor ~8 (pT ~ 50 GeV)
-  Electron identification and measurement
-  For electron efficiency of 80% jet rejection decreases by ~ 50%
-  Muon identification and measurement
-  If enough shielding is provided expect reconstruction efficiency and momentum resolution not to deteriorate much
-  Forward jet-tagging and central veto
-  Essential handle to increase S/N for WW and ZZ fusion processes
-  Performance can be significantly degraded – though algorithms could be optimized
-  Trigger
-  High thresholds for inclusive triggers; use of exclusive triggers selecting specific final states.

## Calorimeters: CMS ECAL

**Crystals **
**	****Barrel: OK**
**	****Endcap : 3krad/hr at y=2.6 **
**	****Further studies at high dose rates, long term irradiation**
**Photosensors**
**	****Barrel: APDs – higher leakage current a higher noise ~100 MeV/ch**
**	****Endcaps: VPTs – R&D: on new devices may be needed**
**Electronics**
**	****Barrel: OK**
**	****Endcap: R&D: More rad-hard electronics at |y|~3? **
**Activation: in endcaps reach several mSv/h – access will be difficult**

## Calorimeters: ATLAS LAr

**Space Charge Effects**
- GeV/cm2/s
- Comfortable margin in
-            Barrel. Inner parts of
-            em endcap and FCAL
-            may be affected
**HV Voltage Drop**
- Comfortable margin in
-            Barrel. Small ‘wheel’
-            of em endcap sees a
-            large current
- Precision  meas. not
-      possible
**Electronics**: Probably OK?
** ****R&D**: Use of another cryogenic liquid, with less charge
-       deposited per GeV, or a cold dense gas to address issues
-        of space-charge and HV voltage drop

**Critical density**

**Notes:**
Critical density where charge losses of ~ 1% occur.
Current induced by the drift of electrons and ions in the gap. This current circulates in the HV chain which incorporates resistors to isolate channels hooked onto the same HV supply. The expected voltage drop is 

## Muon System

**Current ATLAS/CMS muon systems designed with safety factor of 3-5 w.r.t. background estimations (establish real safety margin once LHC operates)**
**Strong geometric dependence of radiation rates , **
**Possible strategy: **
** ****extra shielding at high |y| reduces background everywhere**
** ****restrict high |y| limit of muon acceptance **
**Radio-activation at high |y| of shielding, supports and nearby detectors - may limit maintenance access**
**Balance  super robust detectors  vs  shielding and reduced high- |y| acceptance**
**R&D: Study limit of current detectors - use of CSCs in barrel,**
**     ****at high- |y| - higher rates – use straw chambers? MSGCs/GEMs**?

## Level-1 Trigger

**Trigger Menus**
** ****Triggers for very high p****T**** discovery physics: no rate problems – higher p****T**** thresholds**
** ****Triggers to complete LHC physic program: final states are known – use exclusive menus**
** ****Control/calibration triggers with low thresholds (e.g. W, Z and top events): prescale**
**Impact of Reduced Bunch Crossing Period**
** ****Advantageous to rebuild L1 trigger to work with data sampled at 80 MHz **
** ****Could keep some L1 trigger electronics clocked at 25 ns**
** ****Require modifications to L1 trigger and detector electronics**
**R&D Issues**
** ****Data movement is probably the biggest issue for processing at 80 MHz sampling****	**
** ****Processing at higher frequencies and with higher input/output data rates to the processing elements. Technological advances (e. g. FPGA ) will help**
** ****Synchronization (TTC) becomes an issue for short x-ing period**

## DAQ

**Continuous and extraordinary evolution of computing and communication technologies – monitor the evolution of:**
**Readout Network**
** ****Follow LHC machine luminosity – exploit parallel evolution of technologies**
** ****main building block of DAQ is the switch – interconnecting data sources (event digitizers) and processing nodes (event filters)**
** ****rapid progress in interconnection technologies started recently – LHC needs cannot yet be satisfied using a completely off-the-shelf system **
** ****Technology Tracking**
** ****Complexity Handling**
** ****Online computing systems will have ~ 10000 CPUs, issues of hardware and software management, reliability,remote access, security, databases **
** ****Technology Tracking  (e.g. those found in ISPs) **
** ****R&D: How to handle bandwidth (rate  size) Bandwidth is an issue both for readout and for event building**