ATLAS first run scenarios for B physics

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ATLAS first run scenarios for B physics
Paula Eerola, Lund University On behalf of the
ATLAS collaboration Beauty 2006, Oxford, 25-29
September 2006
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This talk includes

• Introduction
• A summary of the LHC start-up scenario
• B-production in the LHC commissioning run (450
  GeV 450 GeV) until the end of 2007.
• The first physics run at 14 TeV
• Role of B-physics and Heavy Quarkonia events in
  understanding the detector, trigger and
  online/offline software with 100 pb-1.
• Strategies for B-physics with 100 pb-1 - 1 fb-1

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Introduction

• ATLAS is a general-purpose experiment, with an
  emphasis on high-pT physics beyond the Standard
  Model.
• ATLAS has also capabilities for a rich B-physics
  programme, thanks to precise vertexing and
  tracking, high-resolution calorimetry, good muon
  identification, and a dedicated and flexible
  B-physics trigger scheme.
• ATLAS has a well-defined B-physics programme for
  all stages of the LHC operation, from the
  commissioning run all the way up to the highest
  luminosity running.

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ATLAS B-physics goals precision measurements and
new physics

• CP-violation parameters
• B-hadron parameters masses, lifetimes, widths,
  oscillation parameters, couplings, b-production,
  etc.
• Search for New Physics effects very rare decay
  modes, forbidden decays/couplings, etc.

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News from the LHC machine
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New LHC machine schedule

• P. Jenni ATLAS Overview Week July 2006
• A new LHC schedule and turn-on strategy was
  presented to the CERN SPC and Council June 2006.
  The main features of the new schedule are
• The beam pipe closure date will be end of August
  2007.
• LHC commissioning run with collisions at the
  injection energy (vs 900 GeV), scheduled
  November 2007. Luminosity typically L
  1029cm-2s-1.
• During the commissioning run at 900 GeV the LHC
  will be a static machine, no ramp, no squeeze, to
  debug the machine and the detectors.
• Then there will be a shut-down (typically 3
  months) during which the remaining machine
  sectors will be commissioned without beam to full
  energy (vs 14 TeV).
• After that the LHC will be brought into
  operation for the first physics run at 14 TeV,
  with the aim to integrate substantial luminosity
  by the end of 2008 goal several fb-1 by the end
  of 2008.

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The commissioning run

• The run in 2007 will primarily be a detector and
  computing commissioning run, much more than a
  physics run.
• A few weeks of stable running conditions at the
  injection energy.

• b cross section dominates at both vs 900 GeV
  and 14 TeV.
• At vs 900 GeV the b fraction of total inelastic
  events is 10 x smaller than at 14 TeV.

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Triggers for the commissioning running

• vs 0.9 TeV, L 1029cm-2s-1, sinel40 mb ltgt 4
  kHz interaction rate
• Commissioning the detector, the trigger, the
  offline reconstruction and analysis chains
• Data taking with loose level-1 (LVL1) single muon
  triggers (pTgt5 GeV) or minimum bias triggers
• The High Level Trigger (HLT) in pass-through mode
  for testing
• See J. Kirks talk on ATLAS triggers

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Rates and statistics
vs 900 GeV, L1029cm-2s-1
Decay Rate N(ev) for 1 d N(ev) for 30 d
Min bias hadron ? m5 X hmlt2.5 1400 10-4 Hz 3 600 109 000
b ? m5 X 60 10-4 Hz 150 4 700
b ? m5 m3 X 2 10-4 Hz 5.2 150
b ? J/y ( m5 m3 ) X 0.1 10-4 Hz 0.3 8
pp ? J/y ( m5 m3 ) X 1 10-4 Hz 3 80
pp ? ? ( m5 m3 ) 1.7 10-4 Hz 4.4 130
) 1 full day is 8.64 104 s, 30 machine and
data taking efficiency assumed
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Event statistics with B and Quarkonium muonic
decays
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Event statistics for the commissioning run
30 data taking efficiency included. Efficiency
of trigger and analysis cuts included.
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Conclusions for the commissioning run

• Heavy flavours b and c will be a source of 4.7k
  single muons and 370 di-muons given 30 days of
  beam (30 machine and data taking efficiency).
• Soft LVL1 single-muon trigger can be used to
  select those events.
• High-level trigger in pass-through mode.
• The dimuon sample includes about 90 J/y(m5m3) and
  130 ? (m5m3) can serve for first tests of mass
  reconstruction.
• Any heavy flavour physics? Low statistics will
  not allow separating direct and indirect J/y
  sources. S/B a factor of 10 worse than at the
  nominal LHC c.m. energy. Muons from hadron decays
  dominate the trigger rate due to worse S/B and
  softer spectrum. The ratio of J/y and ? - events
  may be the best bet.

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The first physics run B-physics strategies
- Serve as a tool for understanding the trigger
and the detector calibration, alignment,
material, magnetic field, event reconstruction.-
Physics cross-section measurements at new energy
- QCD tests and optimization of B-trigger
strategies.- Control B-channels will be used to
verify if we measure correctly well known
B-physics quantities (with increasing integrated
luminosity ? real measurements).- Control
B-channels will also be used to prepare for
high-precision B-measurements and searches for
rare decays tagging calibration, production
asymmetries, background channels specific for
rare decays.
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Trigger priorities for the first physics running

• vs 14 TeV, L 1032-33cm-2s-1
• Many customers for the data
• Data for commissioning the detector, the trigger,
  the offline reconstruction and analysis chains
• Data samples high-pT physics studies
• Data samples for B-physics studies
• Scope depends on luminosity and available HLT
  resources
• Data samples for minimum-bias physics studies
• Needed also for tuning Monte Carlo generators
  used in other physics studies

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Trigger menus for B-physics

• The ATLAS B-physics programme is based on LVL1
  muon triggers
• Inclusive low-pT single-muon triggers at low
  luminosity
• Low-pT dimuon triggers at higher luminosities
• Search for specific final states (exclusive or
  semi-exclusive) in HLT
• Refine muon selection, then
  reconstruct tracks from B decays in
  the inner detector (ID)
• Tracks in ID track search in the full
  ID or in regions given by LVL1
  Regions of Interests
  (RoIs), depending on the
  HLT processor capacity and luminosity
• See J. Kirk

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B cross-section at LHC

• All LHC experiments plan to measure B-cross
  section in proton-proton collisions.
• Measurements will cover different phase space
  will be complementary.
• Partial phase-space overlaps LHCb, ATLAS, CMS,
  ALICE - opportunity for cross-checks.
• Methods of measurement for low- and medium-pT
  events in ATLAS
• b ? m6 X
• b ? m6m3 X
• Exclusive channels B?J/y K, B0? J/y K0
• b- correlations B?J/y X b? m

Dff J/y - fm
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Statistics for cross-section and correlation
measurements
Decay Statistics with 10 pb-1 Statistics with 100 pb-1
b ? m6 X 40 M 400 M
c ? m6 X 20 M 200 M
b ? m6 m3 X 2 M 20 M
B ? J/y(m6m3) X and b ? m5 X 2 500 25 000
B?J/y K 1 700 17 000
B0? J/y K0 870 8 700
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B-physics with 100 pb-1 J/y and ?
Decay Statistics with 100 pb-1 Measurement
pp ? J/y(m6m3) 1000 k R(b ? J/y )/R( pp ? J/y) R(pp ? U) /R( pp ? J/y)
b ? J/y(m6m3)X 400 k R(b ? J/y )/R( pp ? J/y) R(pp ? U) /R( pp ? J/y)
? (m6m3) 100 k R(b ? J/y )/R( pp ? J/y) R(pp ? U) /R( pp ? J/y)
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B physics with 100 pb-1 exclusive B decays
Decay Statistics with 100 pb-1 Measurement
B?J/y K 17 000 Important reference and control channel new channels (B?mm) relative to this.
B0? J/y K0 8 700 Control channels masses, lifetimes etc. Sensitive checks for understanding the Inner Detector.
B0? J/y Ks 1 300 Control channels masses, lifetimes etc. Sensitive checks for understanding the Inner Detector.
Bs? J/y f 900 Control channels masses, lifetimes etc. Sensitive checks for understanding the Inner Detector.
Lb? J/yL 260 Control channels masses, lifetimes etc. Sensitive checks for understanding the Inner Detector.
Bs ? Ds p 25 Hadronic channels only prepare methods for later measurements.
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The reconstructed masses and lifetimes of the
well-known control channels are sensitive tests
of those detector features which have a strong
impact on B-physics measurements.
Lifetime reconstruction with control channels
Decay Statistics 100 pb-1 Statistical error on lifetime World av today (stat syst)
B B?J/y K 17 000 1.5 0.4
B0 B0? J/y K0 8 700 2.2 0.5
Bs Bs? J/y f 900 6 2
Lb Lb? J/yL 260 8 5
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B physics with 100 pb-1 sensitivity to rare
exclusive B decays
Decay Statistics or limit with 100 pb-1 Measurement today
B?mm K 23 Belle today 80?
B0? mm K0 12 Belle today 80?
Bs? mm f 9
Lb? mmL 3
Bs?mm 6.410-8 at 90 C.L. CDF currently 8.0x10 -8 at 90 C.L.
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B0s? µµ- with 100 pb-1, 10 fb-1 and 30 fb-1
Discovery channel B0s? µµ-
Integrated LHC luminosity N(signal) after all cuts N(backgr.) after all cuts ATLAS upper limit for Br(B0s? µµ- ) at 90 C.L. CDF upper limit for Br(B0s? µµ- ) at 90 C.L.
100 pb-1 0 0.2 6 10-8 8.010-8
10 fb-1 7 20 1.210-8 8.010-8
30 fb-1 21 60 7 10-9 8.010-8
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Conclusions

• Commissioning run at 900 GeV, very low luminosity
  
• Commissioning of the detector, the trigger, the
  offline reconstruction and the analysis chains.
• In 30 days 4.7k single muons and 370 di-muons
  from b and c first tests of trigger and offline
  muon reconstruction.
• 90 J/y and 130 ? first tests of mass
  reconstruction.
• First physics run at 14 TeV, 100 pb-1 1 fb-1
• Measurements of B masses and lifetimes a
  sensitive test of understanding the detector
  alignment, material, magnetic field, event
  reconstruction etc.
• Cross-section measurements at new energy QCD
  tests and also optimization of B-trigger
  strategies.
• J/Y and ? measurements.
• Control B-channel measurements to prepare for
  further B physics precision measurements and
  new physics measurements.
• With 100 pb-1 ATLAS can achieve a sensitivity of
  6.410-8 in the discovery channel Br(B0s? µµ- ),
  which is at the level of current Tevatron results.

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• Thank you!

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BACKUP SLIDES
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Cross sections in ATLAS for muonic channels
Process Cross-section at vs 14 TeV Cross-section at vs 14 TeV Cross-section at vs 900 GeV Cross-section at vs 900 GeV
Total LHC bb cross section 500 mb 25 mb
Total LHC inelastic s 70 mb 40 mb
Min bias hadron ? m6(5) X hmlt2.5 10 000 nb 1 400 nb
b ? m6(5) X 4 000 nb 60 nb
b ? m6(5) m3 X 200 nb 2 nb
b ? J/y ( m6(5) m3) X 7 nb 0.1 nb
pp ? J/y ( m6(5) m3 ) X 28 nb 1 nb
pp ? ? ( m6(5) m3 ) 9 nb 1.7 nb
) Dimuon pT cuts for muon reconstruction and
identification are (6, 3) GeV at 14 TeV and
(5, 3) GeV for 900 GeV. For both muons hlt2.5.
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Sources of low-pT single and double muons
LVL1 muon trigger rates _at_ 14 TeV and 1033cm-2s-1

• The figure shows sources of low-pT muons at 14
  TeV.
• Muons from hadron decays in flight (h in the
  figure) have a softer spectrum than muons from b.
• At 900 GeV their relative contribution is larger
  b fraction of total inelastic cross section
  10 smaller than at 14 TeV.

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Cross sections for several dominant channels in
LHC (yellow) and in ATLAS volume (rest).
14 TeV 900 GeV
Total LHC inelastic (NSD) s 70 mb 40 mb
Total LHC bb cross section 500 mb 25 mb
jet pTgt15GeV hlt2.5 24 mb
Min bias ? m6(5) X hmlt2.5 10000 nb 1400 nb
b-jet pTgt15GeV hlt2.5 370 nb
jet pTgt50 GeV hlt2.5 45 nb
bb ? m6(5) X hmlt2.5 4000 nb 60 nb
bb ? m6(5) m3 X hmlt2.5 200 nb 2 nb
pp ? ? ( m6(5) m3 ) hmlt2.5 9 nb 1.7 nb
pp ? J/y ( m6(5) m3 ) X hmlt2.5 28 nb 1 nb
b-jet pTgt50 GeV hlt2.5 0.63 nb
bb ? J/y ( m6(5) m3 ) X hmlt2.5 7 nb 0.1 nb
) m6(5) - muon pT cuts for 14TeV (900 GeV)
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900 GeV 1029cm-2s-1 rates, statistics
rates 30d 106s
jet pTgt15GeV hlt2.5 24 10-1 Hz 2 400 000
Min bias ? m5 X hmlt2.5 1400 10-4 Hz 140 000
b-jet pTgt15GeV hlt2.5 370 10-4 Hz 37 000
jet pTgt50 GeV hlt2.5 45 10-4 Hz 4 500
bb ? m5 X hmlt2.5 60 10-4 Hz 6 000
bb ? m5 m3 X hmlt2.5 2 10-4 Hz 200
pp ? ? ( m5 m3 ) hmlt2.5 1.7 10-4 Hz 170
pp ? J/y ( m5 m3 ) X hmlt2.5 1 10-4 Hz 100
b-jet pTgt50 GeV hlt2.5 0.63 10-4 Hz 63
bb ? J/y ( m5 m3 ) X hmlt2.5 0.1 10-4 Hz 10
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Event statistics with B and Quarkonium muonic
decays
vs 900 GeV, L1029cm-2s-1
bb ? m5 X
bb ? m5m3 X
pp ? ? (m5m3) X
ppbb ? J/y (m5m3) X
40 machine and data taking efficiency assumed.
No reconstruction efficiencies included.
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30 data taking efficiency included. Efficiency
of all analysis cuts included.
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Detector configuration during the first physics
run

• B-layer OK.
• ID complete, only TRT C-wheels staged
• HLT configuration full 45kHz LVL1 capacity.