SuperLHC

1
SuperLHC
Physics Potential and Experimental Challenges of
the Luminosity Upgrade LHCC, CERN, 27 November
2002
Machine Upgrade The Expected Detector
Performance Physics Potential Experimental
Challenges and Detector RD Conclusions
Tejinder S. Virdee CERN/Imperial College
2
References
Talks by F. Gianotti, D. Green and F. Ruggiero
at the ICFA Seminar (Oct 2002)
3
The Machine Upgrade

• What is a Super LHC ?
• Upgrade luminosity target L 1035 cm-2s-1
• Upgrade energy up to 28 TeV !
• This talk deals with the option that has
• moderate extra cost (10-15) relative to initial
  LHC investment
• would be implemented 5-6 years after LHC
  physics startup
• Upgrade in 3 main Phases
• Phase 0 maximum performance without hardware
  changes
• Phase 1 maximum performance while keeping LHC
  arcs unchanged
• Phase 2 maximum performance with major
  hardware changes to the LHC
• Reminder LHC Nominal baseline parameters L
  1034 cm-2s-1 _at_ 7 TeV _at_ 1.1.1011 p/bunch

4
Machine Challenges
Nominal LHC performance is already very
challenging. Limiting factors are Dynamic
aperture by main dipole field quality (limits the
emittance at injection), crossing angle Single
beam intensity by collective effects electron
cloud effects (scale linearly with bunch
spacing), cryogenic heat load Peak luminosity by
non-linear beam-beam interactions detuning
caused by head-on and parasitic collisions in all
IPs Luminosity lifetime by pp interaction rate,
beam-gas, transverse blow-up due to intra-beam
scattering Integrated luminosity by luminosity
lifetime, operations Energy by maximum bending
field
5
Phase 0
Phase 0 maximum performance without hardware
changes
1) Collide beams only in IP1 and IP5 (no
collisions in IP2 and IP8) 2) Increase
protons/bunch up to ultimate intensity (1.7.1011
p/bunch) ? L 2.3 1034 cm-2s-1 3)
Optionally increase main dipole field to 9T
(ultimate field) E g 7.5 TeV
6
Phase 1
Phase 1 maximum performance while keeping LHC
arcs unchanged Change LHC insertions and/or
injector complex

• 1) Reduce ? ( from nominal 0.5 m to 0.25 m, say)
• 2) Increase crossing angle (from nominal 300 mrad
  by a factor of about ?2)
• 3) Increase protons/bunch up to ultimate
  intensity (1.7.1011 p/bunch)
• L 3.3 1034 cm-2s-1
• 4) Halve bunch length (new RF system) ? L 4.7
  1034 cm-2s-1

7
Phase 2
Phase 2 maximum performance with major hardware
changes to the LHC
1) Reduce ? ( from nominal 0.5 m to 0.25 m,
say) 2) Increase crossing angle (by a factor of
about ?2) 3) Increase protons/bunch up to
ultimate intensity ? L 3.3 1034
cm-2s-1 (not beam-beam limited) 4) Halve bunch
length ? L 4.7 1034 cm-2s-1 5) Double number of
bunches ? L 9.4 1034 cm-2s-1

• (5) is thought to be v. difficult due to the
  electron cloud effect.
• Reach 1035 by employing a superbunch (300m
  long) but probably excluded from point of view of
  experiments (higher no. of superbunches ?).
• Another way is to equip SPS with s.c. magnets
  and inject into LHC at 1 TeV
• a increase LHC luminosity by factor 2.

8
RD for the Machine

• Low b insertion sections (separation dipoles,
  triplet quads, TAS, TAN )
• high intensity injectors e.g. Super Proton Linac
• cryogenics upgrades
• r.f. upgrades for halving bunch length or
  handling superbunches
• Low cost s.c. magnets for SPS
• RD in beam dynamics
• For energy upgrade low cost high field dipoles

9
Detectors General Considerations
Normalised to LHC values.
104 Gy/year R25 cm
In a cone of radius 0.5 there is ET
80GeV. This will make low Et jet triggering and
reconstruction difficult.
10
Detectors General Considerations
Rapidity plateau shrinks for heavy states For
example Z of 1 and 5 TeV decaying into light
pairs. Wide angle (barrel) detectors more
important.
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Expected Detector Performance

• Tracking and b-tagging
• isolated high pT (gt 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 will be significantly degraded
  though algorithms could be optimised
• Trigger
• high thresholds for inclusive triggers use of
  exclusive triggers selecting specific final
  states, pre-scaling

12
Assumptions Used For Physics Potential

• Detector Performance
• performance at L 1035 cm-2s-1 is comparable to
  that at 1034 cm-2s-1 !!
• Integrated Luminosity per Experiment
• 1000 (3000) fb-1 for 1 (3) year(s) of running
  at L 1035 cm-2s-1.

13
Extending the Physics Potential of LHC

• Higgs physics
• rare decay modes
• Higgs couplings to fermions and bosons
• Higgs self-couplings
• Heavy Higgs bosons of the MSSM
• Strongly-coupled vector boson system
• WLZL g WLZL , ZLZL scalar resonance, WLW L
• Supersymmetry
• New Gauge Bosons
• Extra Dimensions
• Direct graviton production in ADD models
• Resonance production in Randall-Sundrum models
• Resonance production in TeV-1 scale extra
  dimensions
• Black Hole production
• Quark substructure
• Electroweak Physics
• production of multiple gauge bosons (nV .ge. 3)
• triple and quartic gauge boson couplings

14
Higgs Physics Couplings
Couplings can be obtained from rate measured in a
given production channel
Closed symbols LHC 600 fb-1 Open
symbols SLHC 6000 fb-1

• SLHC could improve LHC precision by up to 2
  before first LC becomes operational

15
Higgs Physics Self Couplings
LHC ? (pp ? HH) lt 40 fb mH gt 110 GeV
small BR for clean final states ? no
sensitivity SLHC HH ? W W- W W- ? ?? ?jj
???jj studied (very preliminary)
-- HH production may be observed for first
time at SLHC -- ? may be measured with stat.
error 20
Not competitive with LC precision up to 7 (?s
? 3 TeV, 5000 fb-1)
16
Supersymmetry
If SUSY stabilises mH ? TeV-scale ? easy and
fast discovery at LHC
In addition measurements of many sparticle
masses to 1-10 ? first constraints of
underlying theory
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SUSY Higgs Physics
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Strongly Coupled Vector Boson System
If no Higgs, expect strong VLVL scattering
(resonant or non-resonant) at

• Difficult at LHC
• At SLHC
• degradation of fwd jet tag and central jet veto
  due to huge pile-up
• BUT factor 10 in statistics ? 5-8? excess in
  WL WL scattering
• ? other low-rate channels accessible

19
Extra Dimensions at (S)LHC
A black hole event with MBH 8 TeV in
ATLAS Spectacular signature !
ADD Gg g Jet Etmiss RS G g ll KK excitations
of g, Z etc.
Black holes decay immediately (? 10-26 s) by
Hawking radiation (democratic evaporation)
large multiplicity, small missing E,
jets/leptons 5
20
Indicative Physics Reach
Fabiola Gianotti ICFA Seminar
Units are TeV (except WLWL reach) ?Ldt
correspond to 1 year of running at nominal
luminosity for 1 experiment
PROCESS LHC SLHC
VLHC VLHC LC
LC 14 TeV
14 TeV 28 TeV 40 TeV 200 TeV
0.8 TeV 5 TeV
100 fb-1 1000 fb-1 100 fb-1 100 fb-1
100 fb-1 500 fb-1 1000 fb-1 Squarks
2.5 3 4
5 20 0.4
2.5 WLWL 2?
4? 4.5? 7?
18? 90? Z
5 6
8 11 35
8 30 Extra-dim (?2)
9 12 15
25 65 5-8.5
30-55 q
6.5 7.5 9.5
13 75 0.8 5 ?
compositeness 30 40
40 50 100 100
400
Approximate mass reach of pp machines ?s 14
TeV, L1034 (LHC) up to ? 6.5 TeV ?s
14 TeV, L1035 (SLHC) up to ? 8 TeV
?s 28 TeV, L1034 up to ?
10 TeV ?s 40 TeV, L1034
up to ? 13 TeV ?s 200 TeV, L1034 (VLHC)
up to ? 75 TeV
indirect reach (from precision measurements)
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Detector Considerations

• Can the current detectors survive at a luminosity
  of 1035cm2 s1?
• If not, what are the possible replacement
  detectors/technologies ?
• What are the technological challenges ?
• Assuming that the detectors need to be ready and
  installed in 2012
• When should the RD start taking account of the
  manufacturing phase?
• What priority would you assign to the RD?
• What resources would be required (financial and
  manpower)?
• How would the RD interface with that carried out
  elsewhere?

22
ATLAS
23
CMS
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Inner Tracking
The inner tracker will probably need to be
changed as a whole Preserve current pattern
recognition, momentum resolution, b-tagging
capability a cell sizes have to be decreased by a
factor 10
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Inner Tracking RD 1

• Region 1 r lt 20cm
• Occupancy g Need pixels of a size factor 5
  smaller than used today
• (125x125 mm2 g 50 x 50 mm2) g benefit
  b-tagging
• RD 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
• Study the limits of hybrid pixels approach ?
• Region 2 20ltrlt60 cm
• Need cell sizes 10 times larger than current
  pixels but at 10 times lower cost/channel than
  current Si microstrips g benefit p-resolution and
  pattern
• Si Macro-pixels of an area lt 1mm2 pads or
  shorter mstrips ?
• Could be upgrades of innermost Si microstrip
  layers of current detectors
• RD to demonstrate low-cost macro-pixels
  concept, thin Si detectors, signal routing ?

26
Inner Tracking RD 2
Region 3 r gt 60 cm Si-strips decrease size of
strips i.e. increase no. of channels by gt 50 Use
standard radiation resistant mstrip
technology RD Feasibility of processing
detectors on 8 or 12 Si wafers Engineering RD
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 RD 4 years of build, 4 years
of RD and prototyping ?
27
Calorimeters CMS ECAL
CMS ECAL Integrated Luminosity of 2500 pb-1
Crystals Barrel OK Endcap 3krad/hr at
h2.6 Further studies at high dose rates, long
term irradiation Photosensors Barrel APDs
higher leakage current a higher noise 100
MeV/ch Endcaps VPTs RD on new devices may
be needed Electronics Barrel OK Endcap RD
More rad-hard electronics at h3? Activation in
endcaps reach several mSv/h interventions will
be difficult
28
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? RD 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
29
Other Calorimeters
HCAL Integrated Doses Barrel 2kGy, Endcap up
to 500 kGy _at_ h2.9! Fe or Brass/scintillator ATLA
S Only in the barrel so should be OK CMS
Barrel OK, Endcap periodic replacement ?
separate readout of initial layers ? RD find
an alternative to plastic scintillator Forward
Calorimeters Integrated Dose can reach 10 MGy
! ATLAS RD dense cold gas CMS RD
quartz-clad quartz fibres, pressurised gas
Cerenkov radiator ?
30
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 particle and
  radiation induced rates
• a detector types that function at high-h at LHC
  will function at low-h in SLHC
• Possible strategy
• extra shielding at high h g reduces background
  everywhere
• restrict high h limit of muon acceptance
• (may force re-design of other sensitive
  sub-systems eg CMS endcap HCAL)
• Radio-activation at high h of shielding, supports
  and nearby detectors
• - may limit maintenance access
• Balance super robust detectors vs shielding
  and reduced high-h acceptance
• Cost-benefit analysis depending on the physics
  potential
• RD Study limit of current detectors - use of
  CSCs in barrel,
• At high-h - higher rates use straw chambers?
  MSGCs/GEMs?

31
Neutron Fluxes in CMS Muon Endcaps
High-h region of CMS endcap muon
detectors Neutron flux in n/cm2/s) Top
acceptance h lt 2.4 present shielding L1034
cm-2 s-1 Bottom acceptanceh lt 2.0 Possible
shielding L1035 cm-2 s-1
32
Level-1 Trigger

• Higher L a higher occupancy, increased trigger
  rates at fixed pT thresholds (higher thresholds
  for fixed rates) a physics impact
• Trigger Menus
• Triggers for very high pT discovery physics no
  rate problems higher pt thresholds
• Triggers to complete LHC physic programme final
  states are known use exclusive menus
• Control/calibration trioggers with low
  thresholds (e.g. W, Z and top events) prescale
• Impact of Reduced Bunch Crossing Period
• Advantageous to rebuild LVL1 trigger to work
  with data sampled at 80 MHz (internally some data
  movement and/or processing are already done at 80
  MHz)
• Could keep some LVL1 trigger electronics clocked
  at 25 ns
• Require modifications to LVL1 trigger and
  detector FE electronics
• RD 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, although technological advances (FPGAs,
  etc.) will help
• Synchronization (TTC, etc) becomes an issue for
  short BC period

33
DAQ

• Continuous and extraordinary evolution of
  computing and communication technologies Need
  continuing development programme in
• Readout Network
• Follow LHC machine luminosity exploit parallel
  evolution of technologies
• main building block of DAQ is the switch
  interconnecting data sources (event digitisers)
  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 network technologies should
  be tracked
• Complexity Handling
• Online computing systems will have 10000 CPUs,
  issues of hardware and software management,
  reliability,remote access, security, databases
• Technology Tracking Modern technologies (e.g.
  those found in ISPs) should be studied to control
  distributed computing and exploit web-tools
• RD How to handle bandwidth (rate ? size)
  Bandwidth is an issue both for readout and for
  event building

34
Electronics

• Micro-electronics line-widths decrease by a
  factor 2 every 5 years.
• Today 0.13 mm available commercially
• 0.03 mm in laboratory so know that trend will
  continue for at least 10 more years
• Need to build on/preserve expertise and
  infrastructure employed for current LHC expts
• RD
• Characterise 0.13mm technology (and beyond)
•  more radiation tolerance required dose and
  Single Event Effects
•  advanced high bandwidth data link technologies
• system issues addressed from the start
• NRE invest in new design software (high costs
  gt 1 M)
• CERN has a leading (coordinating) role here

35
Conclusions

• LHC luminosity upgrade can extend
• physics reach of LHC at a moderate extra cost
  relative to initial LHC investment.
• the LHC lifetime and bridge time gap to future
  machine.
• To realise this reach, the LHC detectors must
  preserve performance
• trackers must be rebuilt, and
• calorimeters, muon systems, triggers and DAQ need
  development.
• Upgrades programme, from launch to data taking
  will take 8-10 years
•  
• The time to start is soon. The mains actors have
  necessarily to be the ones who did the original
  RD and today are building the detectors.
• If the path of going to higher luminosities is
  chosen then need to
• launch a detector and accelerator RD programme
  similar to the DRDC one but perhaps more
  directed.
• Current LHC detector technologies were chosen
  after a very successful Detector RD programme
  launched by CERN in early 90s

36
Muon System
Barrel
Endcaps
37
Electroweak Physics

• Triple gauge boson couplings
• indication of non-SM TGCs at LHC then increased
  statistics at SLHC should allow deeper
  understanding of New Physics.
• sensitivity to anomalous TGCs arises from
  increased production cross-section an altered
  angular distributions
• use states containing isolated leptons
  significant detector upgrades not needed.
• meaningful test of corrections e.g. in SUSY
  models

38
Higgs Physics Rare Decays
Channel mH S/?B
LHC S/?B SLHC
(600 fb-1)
(6000 fb-1) H ? Z? ? ??? 140 GeV
3.5 11 H ? ??
130 GeV 3.5 (ggVBF) 7
(gg)
BR 10-4 both channels
additional coupling measurements e.g. ?? /?W
to 20
39
Activation