Impact of WarmCold Technology Choice

1
Impact of Warm-Cold Technology Choice on LC
Physics and Detector
Mike Woods, SLAC
Victoria Linear Collider Workshop July 28-31, 2004
2
Warm-Cold Differences in Beam Parameters
Bunch Timing
Bunch Charge
Beamstrahlung
Bunch Length
Energy Spread
Crossing Angle?
3
Warm-Cold Differences in Beam Parameters
4
Warm-Cold Impact on Detector and Physics?
Detector Speed, Pileup and Resolution?
Backgrounds?
Hermeticity?
EMI and RF Pickup?
DAQ and Trigger?
Energy Precision?
Physics Analyses Statistical Errors?
Systematic Errors?
5
International Technology Recommendation Panel
Detector and Physics Issues
Agenda for ITRP Meeting at CalTech June 28, 2004
Energy Spread Tim Barklow Crossing
Angle Philip Bambade Bunch Timing (Cold
Perspective) Klaus Moenig Bunch Timing (Warm
Perspective) Hitoshi Yamamoto
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Worldwide Study
Detector and Physics Issues
Talks presented at CalTech ITRP Meeting, see
http//www.ligo.caltech.edu/donna/ITRP_mt5.htm
more info for CalTech presentations, see
http//www-zeuthen.desy.de/TESLA/itrp/itrp_det.htm
l Related talks at this meeting MDI
Session Thursday 1030-1230 Physics impact
of beam energy spread and precision, Tim
Barklow Joint MDI/Tracking Session
Thursday 1330-1500 Pair Backgrounds and
Electron ID for a 2-photon Veto, Takashi
Maruyama TPC Timing and Background Sensitivity,
Mike Ronan Detector occupancies and Energy
resolution effects, Norman Graf Timing and
signal processing in Si detectors, David Strom
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Energy Spread
Energy Bias Effects Effects on Physics
Analyses top threshold, Higgs recoil mass,
chargino threshold, smuon mass
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Lumi, Energy Measurement Goals

• Luminosity, Luminosity Spectrum
• Total cross sections absolute dL/L to
  0.1
• threshold scans core width to lt0.05 ECM
• and tail population dL/L to lt1

• Center of Mass Energy
• Smuon mass 1000 ppm (24 Mev for 220
  GeV smuon)
• Top mass 200 ppm (35 Mev)
• Higgs mass 200 ppm (25 MeV for 120 GeV Higgs)
  

The optional Giga-Z program requires better
precision for luminosity and beam energy
measurements, such as dEcm/Ecm 50 ppm for 5
MeV W mass measurement or 10-4 (absolute) ALR
measurement.
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Luminosity measurements from small angle Bhabhas
at polar angles of 40-120 mrad. expect
similar precision for warm/cold Lumi spectrum
measurements from Bhabha acolinearity at
polar angles of 200 mrad or greater expect
similar precision for warm/cold Energy
measurements from upstream BPM spectrometer
or downstream Synchrotron-stripe
spectrometer. expect similar precision for
warm/cold
10
The beam energy spectrometers measure ltEgt, but
for physics we need to know ltEgtlum-wt and the
luminosity spectrum, L(E).
The largest source of bias are ISR and
beamstrahlung. ISR can be calculated to high
precision. Beamstrahlung is similar
for warm/cold and its effects can largely be
determined from a Bhabha acollinearity analysis.
An energy bias also arises from a combination of
beam energy spread, bunch E-z correlation, and
the collision y-z kink instability.
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Beam Energy Profiles
Before Collision
Lumi Weighted
After Collision
WARM
COLD
Ebeam (GeV)
Ebeam (GeV)
Ebeam (GeV)
12
Wakefields, Disruption and y-z Kink instability
Linac wakefields generate banana beam
distortions (larger for NLC than for TESLA)
TESLA example
NLC example
(larger for TESLA than for NLC)
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E-Z Cor, Y-Z Kink Instability and ECM Bias
(larger for COLD)
(comparable at WARM, COLD)
(larger for WARM)
Wakefields Disruption Y-Z Kink
instability
Summary of ECMbias
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NLC (P. Tenenbaum and A. Seryi, LCC-139)
Alternate BNS Setup for NLC Leads to Smaller
Espread Ebias

• 3 BNS Phases (nominal)

E30 GeV
Eswitch170 GeV

• Can reduce energy spread and Ebias
• by decreasing the energy of final
• switch point (120 GeV optimal)

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NLC
TESLA
Summary of ECMbias
NLC
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(Study by T. Barklow)
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Ecm Measurement
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(Study by T. Barklow)
Statistical Errors
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(Study by T. Barklow)
Statistical Errors
WARM
COLD
Smuon Energy (GeV)
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Simdet Detector Simulation of ee- ? Zh
(Study by T. Barklow)
WARM
Recoil Mass Statistical Errors
COLD
Best Higgs mass measurement will come from 4-jet
final state (shown later)
MSSM theory error on Mh (S. Heinemeyer at LCWS
04, Paris)
Recoil Mass (GeV)
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Crossing Angle
Post-IP Beam Diagnostics Beam Steering w/
crossing angle from solenoid Hermeticity and
2-photon veto
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Context

• warm LC ?c mrad ? 20 , 7
• cold LC ?c mrad ? 20 , 7 ,
  0
• magnitude important aspect of machine design
• TRC recommended (R2 item) that the technical pros
  / cons of the TESLA head-on scheme especially
  the extraction be critically reviewed and to
  consider also designs with a finite ?c e.g.
  20, 7 mrad or eventually other possibilities (0.6
  and 2 mrad)
• LC scope calls for 2 e?e? IR with similar energy
  and luminosity, one of which with ?c 30 mrad to
  enable a future ??-collider option

23
Energy Spectrometers
24
Polarimeters
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Importance of post-IP Beam Diagnostics

• Different systematics
• Reduced Errors ? v2 improvement possible
• Beam-beam effects can be measured
• Different design constraints relaxed tolerances
  for
• emittance preservation and Detector
  backgrounds

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IP Crossing Angle and Solenoid Effects
ee- collisions
e-
e
qc 10 mrad
Beams still collide head-on
SiD with B 5T, qy 100 mrad
(Reference A. Seryi and B. Parker, LCC-143)
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IP Crossing Angle and Solenoid Effects
e-e- collisions
e-
e-
qc 10 mrad
Beams collide with vertical qC
y
SiD with B 5T, qy 100 mrad
e-
e-
(Reference A. Seryi and B. Parker, LCC-143)
qy
z
Significant Luminosity loss, unless additional
compensation provided!
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IP Crossing Angle and Solenoid Effects

• Spin precession and misalignment of Compton IP to
  collider IP
• will have 100 mrad bend angle between Compton
  IP (upstream or downstream)
• and collider IP
• angle is small compared to disruption angles,
  but still undesirable

• Three reasons to compensate the resulting
  vertical steering
• want no vertical crossing angle for e-e-
  collisions
• alignment of extraction line should be
  energy-independent
• want no net bend angle wrt upstream or
  downstream polarimeters

• Compensation techniques
• additional vertical bends
• serpentine solenoid winding (add vertical bend
  to solenoid field BNL work)

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Compensation of Solenoid Steering Effects w/
Crossing Angle

• Adds 0.01 of Bz along x in detector
• TPC tracking ? map Bz to 0.0005 to control
  distortions
• Larger backgrounds and steering of the spent
  beam
• steering compensated with external dipoles

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SUSY, Dark Matter and the Crossing Angle
Dark matter SUSY scenarios ? slepton
neutralino masses often very close
(co-annihilation mechanism)
M. Battaglia et al. hep-ph/0306219
Ex search measure stau with ?m(? - ?) ? 3 9
GeV
if ?c ? 0, ? harder to eliminate 2- ? backgrounds
P.Bambade et al., hep-ph/0406010
signal major
background ee ? ? ?0 ? ?0
ee ? (e)(e) ? ? ?
10 fb ? 106 fb
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Pair Backgrounds and 2-photon Veto ( Pairs for
Beam Diagnostics)
TESLA study, energy deposited by pairs in BEAMCAL
2X larger with qC 20 mrad
energy deposition has more complex shapes ?
beam parameter extraction more complicated
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Collimation ? exit hole radius ? vertex detector
radius
for crossing angle, smaller background
enhancement wrt headon if outgoing hole is
increased also helps relax collimation
requirements
if collimation requirements impose to increase
the exit hole, then the vertex detector radius
would increase as well in the head-on case
GeV / cm2
GeV / cm2
TESLA head-on
TESLA ?c 20 mrad
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Total pair energy for ?c ? 20, 7, 0 mrad
T. Maruyama
cold Rincoming Routgoing
cold Rincoming Routgoing
out-going hole radius cm
out-going hole radius cm

• (Warm R?2cm, 20mrad w/ Serpentine) (Cold
  R?1.2cm, 0mrad)
• Smallest effects for Warm 7mrad
• Total pair energy can be used for luminosity
  monitoring in all cases

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Effect of crossing angle on t mass precision
benchmark point D with ?m?-? 5 GeV
P.Bambade et al., hep-ph/0406010
8 efficiency w/ qC
11 efficiency head-on
Head-on dM/M 0.15 20-mrad dM/M 0.22
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Bunch Timing
Backgrounds Physics Impact of unresolved Bunch
Crossings Detector Occupancies, Time-stamping,
Resolution EMI and Signal Processing
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Beam-Beam Backgrounds (1) Low-energy Pairs from
2-photon events at NLC/GLC
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Beam-Beam Backgrounds (2) Hadronic 2-photon
events at NLC/GLC

• Good timing (1-4 BX) information needed to avoid
  pileup

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Higgs Production from WW-fusion at 1 TeV

• 2 missing neutrinos, no constrained fit possible
• important for model-independent determination
• of partial width H ? WW

(S/B 13.2)
Study by T. Barklow Similar study by K. Desch
et al., LC-PHSM-2004-009
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Higgs Mass with 4-jet Final State
H ? bb, Z ? qq
Study by T. Abe and K. Desch
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Detector Occupancies
Study by T. Abe

• Except for BEAMCAL (5-40 mrad polar angle),
  Detector Occupancies
• are low enough that time-stamping suffices

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Detector Occupancies
Study by T. Abe
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Detector Time-Stamping Capabilities

• Si for Tracking and Calorimetry
• 3-5ns resolution per pad vn reduction for n
  pads hit
• (see talk by Strom in MDI/Tracking)
• TPC
• 2ns T0 resolution with z info from external
  detector (ex. VXD)
• (see talk by Ronan in MDI/Tracking)
• Scintillator Systems
• CDF HCAL achieves 2ns for E gt 4 GeV showers
• KLOE fibre calorimeter achieves 200 ps

43
EndCap Time-stamping Capabilities?
? endcap region is important ? occupancies are
higher time-stamping still works well
Study by T. Abe
Correct timing assignment in Forward ECAL
Correct timing assignment in Forward HCAL
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BEAMCAL at 5-40 mrad polar angle FAST Time
Response Needed!

• Possible Detector Technologies being studied
• Si-W
• Diamond-W
• Gas Cherenkov -W
• Quartz Fiber Cherenkov W
• Gaseous Ionization W

Diamond tested at ATF 20 bunches with 2.8ns
spacing
500 ps/div
Diamond response from a single 12C ion P. Moritz
et al., BI Workshop 1998
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BEAMCAL at 5-40 mrad polar angle High electron ID
efficiency needed for 2-photon veto!
For smaller D(mt mc0), need high efficiency
at smaller radius efficiency can degrade
quickly when integrate over multiple
bunches
(250 GeV more relevant)
Fake rate lt 1
(10 acceptable)
Must cope with large Pair backgrounds
(from K. Moenig)
46
EMI and the Detector Electronics?
Why whisper just when an express train roars
through the station? (C. Damerell at LCWS 2004)
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Concern about rf Pickup Effects for Detector
Readout during Train

• WARM Signal Processing
• All detector subsystems except BEAMCAL (ok)
• Integration times of 1 ms readout between
  trains
• Time-stamping to sub-5ns level per cell
• BEAMCAL
• needs attention for rf Pickup with fast (GHz)
• response/digitization times

• COLD Signal Processing
• VXD
• small signals need to readout 20X per train
• ISIS Image Sensor with In-Situ Storage as
  solution?
• - 800M pixel detector ? 800M x20 pixels!
• Other Systems sensitivity?
• signals larger and signal shaping times may be ok

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Comparison of Beam Parameters affecting EMI

• SLC experience
• 10 ms delay needed before readout of SLDs VXD
  to avoid EMI problems
• source of EMI unknown from rf pickup
  impulse/response to direct
• beam generated noise? or related to other
  electronic signal activity?
• other systems ok, but did not try reading out /
  digitizing within 1 ms of beamtime
• PEP-II experience
• HOM heating scales as (Q/sZ)2
• - relation to EMI for detector electronics?
• - does scaling extend to mm and sub-mm bunch
  lengths?
• - need a cavity of suitable dimensions to excite
• IR geometry (aperture transitions, BPMs) has
  similar complexity as for LC
• VXD and other readout systems ok for EMI in
  signal processing

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Comparison of Beam Parameters affecting EMI

• SLC experience
• 10 ms delay needed before readout of SLDs VXD
  to avoid EMI problems
• source of EMI unknown from rf pickup
  impulse/response to direct
• beam generated noise? or related to other
  electronic signal activity?
• other systems ok, but did not try reading out /
  digitizing within 1 ms of beamtime
• PEP-II experience
• HOM heating scales as (Q/sZ)2
• - relation to EMI for detector electronics?
• - does scaling extend to mm and sub-mm bunch
  lengths?
• - need a cavity of suitable dimensions to excite

Need to learn from PEP-II design/experience Need
to develop deeper understanding of this issue
beam tests?
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Warm-Cold Impact on LC Physics and Detector

• Energy Spread
• Small WARM-COLD differences in STAT error for
  physics channels studied
• 200 ppm precision on lum-wted ECM can be
  achieved for both WARM, COLD
• 50 ppm harder, but configurations such as
  NLC help
• Bhabha acolinearity used to measure energy
  spread and lumi spectrum
• comparable precision for WARM, COLD
• Overall evaluation small advantage for COLD
  (narrower energy spread)
• Crossing Angle
• Beam Instrumentation favors crossing angle
• IR Design, Collimation and Background mitigation
  favor crossing angle
• Hermeticity and 2-photon veto favors head-on
• TRC R2 item for COLD not yet resolved
• Overall evaluation crossing angle preferred
  no WARM-COLD difference
• Bunch Timing
• Good time stamping (1-4 BX) required and
  feasible for WARM
• BEAMCAL needs RD for WARM
• EMI needs more study and evaluation, especially
  for COLD

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Warm-Cold Impact Summary (cont.)

• Energy Reach and Integrated Luminosity determine
  the LC physics reach
• Other beam parameters have a much smaller impact
• Eagerly awaiting the Warm-Cold Technology
  Choice
• Can then consolidate a focused effort on the LC
  Detector designs

Take inspiration from a grand Canadian project
in the late 1800s, that created and unified
Canada from Gordon Lightfoots song and
ballad, Great Canadian Railroad Trilogy
their minds were overflowing with the visions of
their day gotta get on our way, cause were
moving too slow