1. ATLAS, CMS B-Physics Reach UK HEP FORUM The Cosener's House, Abingdon, 24th-25th April 2004 'From the Tevatron to the LHC' M.Smizanska, Lancaster University, UK

2. ATLAS-CMS2 ATLAS,CMS: b-events from central pp LHC collisions 230 b 100 b ATLAS.CMS, LHCb three different strategies to measure B production within partially overlapping phase space LHC pp total = 100 mb inelastic = 80 mb bb = 500 b ATLAS/CMS Central detectors LHCb Forward detector p T after trigger and offline one B in | | < 2.5 p T >10 GeV = 100 b 1.9 < <4.9 p T > 2 GeV = 230 b Luminosity for B physics L = 2 × 10 33 cm -2 s -1 rare B 10 34 cm -2 s -1 L = 2 × 10 32 cm -2 s -1 Statistics exclusive B 1 y @ 10 33 cm -2 s -1 2.6 × 10 6 dominated by B J/ But all hadronic with muon tag 1 y @ 2 × 10 32 cm -2 s - 1 1.7 × 10 6 B J/ 1.7 × 10 6 hadronic

3. ATLAS-CMS3 b-events: LHC vs Tevatron bb - ATLAS/CMS LHCb CDF Bjorken x 1 vs x 2 for events that passed trigger&offline for at least one of B hadrons

4. ATLAS-CMS4 ATLAS/CMS ATLAS b-events: LHC vs Tevatron, cont In hadron-hadron collisions b and anti b quarks are produced with angular distances (0- At LHC a contribution of topologies with b anti b different from back-to back is expected to be even higher than in Tevatron. CDF Implications: B-Trigger strategies Tagging uncertaintes

5. ATLAS-CMS5 ATLAS,CMS B – physics Trigger strategies

6. ATLAS-CMS6 ATLAS Trigger Architecture Hardware (FPGA) General Purpose Processors : offline type algorithms General Purpose Processors optimised algorithms Implementatio n Higher Level Trigger 10 8 10 9 Hz 2 x < 2.5 s ~ 10 ms ~ few sec Decision times FPGA = Field Programmable Gate Array High Level Trigger

7. ATLAS-CMS7 ATLAS,CMS B – physics Trigger strategies Different scenarios for diff. luminosity conditions & rates single-muon di-muon all h h b b c c J/ @10 33 cm -2 s -1 1. Di-muon trigger: L1 2 + L2 full precision tracking B d (B s, B c ) J/ K s 0 (K0*, ), b ( b b ) J/ ( ), B b s 2. Muon-electron( ) trigger: L1 + L1 E/ cluster (E T >2GeV)+ L2 tracking in region B d (B s,B c ) J/ (ee) + K s 0 (K 0 *, ) + B b ( b, b ) J/ (ee) + B b s + B 3. Muon-hadron triggers: L1 + L1 Jet (E T >5GeV) + L2 tracking in region L1 + L2 full-scan tracking in Inner Detector B pure hadronic decays + B

8. ATLAS-CMS8 ATLAS LVL1 Jet RoI LVL1 Jet RoI E T > 6 GeV E T GeV LVL1 Jet RoI E T > 6 GeV B s p T GeV For hadronic final states use LVL1 Jet RoI (events with LVL1 muon) LVL1 Jet Clusters in EM & Hadron Calorimeters. Threshold of E T > 6 GeV (efficient for B s with p T > ~ 16GeV) Final threshold chosen will depend on RoI multiplicity Preliminary simulation studies gives a mean multiplicity of 2 for a 6 GeV threshold (final value may be higher).

9. ATLAS-CMS9 CMS High-Level Trigger Tracking Limited amount of CPU time available for trigger decision: 500 ms on a 1GHz machine possibly 50 ms in 2007 Reduce # of track seeds # of operations per seed Regional seed generation Partial/Conditional Tracking Limited to some region identified by Lvl1 objects (e.g. cone around direction) Stopped when: N hits are reconstructed resolution given threshold P T resolution given threshold given threshold P T value given threshold …………………………………….. …………………………………….. HLT Tracking does not need to be as accurate as in the offline

10. ATLAS-CMS10 CMS B S - + @ L1 : 2 trigger, P T 3 GeV, | | 2.1 @ High Level Trigger: Regional tracking look for pixel seeds only in a cone around the 2, with P T 4 GeV and d 0 1mm, and compatible with PV Conditional tracking reconstruct tracks from good seeds Stop reconstruction if P T 4 GeV @ 5 2%, N hit =6 Keep only tracks with σ(P T )/P T 2%, N hit =6 IF 2 Opposite Signs tracks found Calculate the invariant mass Retain pairs with a) |M -M B S | 150 MeV b) Vertex 2 20 & d 0 150 m Lvl-1 HLT Global Events/ 10fb -1 Trigger Rate 15.2%33.5%5.1%47<1.7Hz

11. ATLAS-CMS11 ATLAS,CMS Inner detector and B-phys performance

12. ATLAS-CMS12 CMS Tracker Design and Performances Pixel around interaction point 4.2, 7, 10 cm and +- 60 cm in z Radius ~ 110cm, Length/2 ~ 270cm 3 disks TID 6 layers TOB 4 layers TIB 9 disks TEC Silicon strip : R = 10-60 m Pixel: R, z = 10-20 m, cell size ~ 100x150 m

13. ATLAS-CMS13 The ATLAS Inner Detector Sub- Detectorr(cm) element sizeresolution hits/track Pixel 5.0; 8.8 50 m x400 m12 m x 60 m 3 (Silicon)12.2 (3D) SCT 30-52 80 m x 12cm 16 m x 580 m4 (Silicon Strip) (stereo) Barrel: 4 cylinders; End-cap: 9 Wheels TRT 56-107 4 mm x 74cm170 m36 (Straw Tubes) (projective) Initial LHC may be without: 1 pixel layer at 8.8cm, one of 3 endcap pixel disks and forward TRT wheels: so called Initial layout Three sub-detectors using different technologies to match the requirements of granularity and radiation tolerance

14. ATLAS-CMS14 ATLAS: Inner detector performance B proper time resolutions Single-Gauss fit [fs] Com plete Initial1998 B s D s 1009867 B 999869 B s J/ 858263 B d J/ K 898669 b J/ 1019573

15. ATLAS-CMS15 Comparison of ATLAS and CMS impact parameter resolutions

16. ATLAS-CMS16 ATLAS particle identification in B-physics events Low pT electron identification Combined EM calorimeter-TRT electron identification Rejection of bb 6X events without electron vs efficiency of events bb 6e5X. Eff=70%,R=570, level-2 rate of signal is 40Hz, fake rate 10Hz due to hadrons misidentified as electrons. TRT electron identification Invariant mass for all track pairs in bb J/ (ee)K 0 events before and after TRT selection cuts. Electrons have pT>1GeV.

17. ATLAS-CMS17 ATLAS particle identification in B-physics events, cont. Low and medium-p T muon performance Lowest pT muon identification & reconstruction efficiency Inner detector + Muon spectrometer Inner detector + Muon spectrometer + Hadron calorimeter J/ ) reconstruction in the environment of b-jet with pT~(50-80) GeV (for QCD b-production studies) the same in log scale Even in high pT jet a mass reconstruction is negligibly affected by fake pairs when a muon identified in Muon spectrometer match to a wrong track in Inner Detector.

18. ATLAS-CMS18 The statistics used in the table includes: dimuon triggers mu6mu3, using LVL1 efficiency 80%/per muon. di-electron LVL2 trigger e1e1. With more realistic e4e4 the precision of ATLAS, CMS degrade by factor 1.2. Method: maximum likelihood fit using experimental inputs: proper time resolution tag probability wrong tag fraction background contribution and composition Neglected at present stage: Direct CP violation term Any new physics contributions Production asymmetry – possibly fcn of (pT Wrong tag fraction – as fcn of (pT Precise measurements of B d J/ K s 0 decay

19. ATLAS-CMS19 Exact: |P/T| 2 Approx: |P/T| 1. Divergencies appeare as sin or cos->1 2. Linear |P/T| approximation is not justified for value 0.36 suggested by current evaluations. 3. The current theoretical uncertainty |P/T|~30% dominates other systematical and statistical errors of full LHC potential. 1. Divergencies appeare as sin or cos->1 2. Linear |P/T| approximation is not justified for value 0.36 suggested by current evaluations. 3. The current theoretical uncertainty |P/T|~30% dominates other systematical and statistical errors of full LHC potential. sensitivity in

20. ATLAS-CMS20 Physics of Bs meson m s from Bs Ds and Bs Ds a 1 already after 1 year sensitivity up to ms - 36 ps -1 fully explore SM allowed range m s (14.3 - 26) ps -1 Program for precise measurements of Bs-anti-Bs system parameters : s, ms and probing Bs mixing phase s allowing to investigate new physics s and s = - from Bs J/ or Bs J/ both sensitive, but precision sufficient only in Bs J/ Angular analyses of cascade decay Bs J/ determine s, s and s simultaneously with 4 parameters of 3 helicity amplitudes A ||, A T, A 0 : A||(t=0), A T (t=0), 1, 2. Parameter ms will be measured by flavor specific decays. Bs

21. ATLAS-CMS21 CP - violation weak phase in Bs J/ Standard Model region-updated 2003 New physics Left-right symmetric model (NP-LR) - needs update (2000 version used here). ATLAS (3y): 1 st level trigger 1 only. 2 1 st trigger under investigation, not included. TDR Detector, 240Evts. ATLAS - same – as above with Initial Detector CMS updated for realistic trigger in 2004 3y@1033 : 252k Evts. The estimated precision between the two ATLAS curves. LHCb(5Y): full 1st Level trigger, performance parameters as given in 2000 Experimental potential of both experiments not yet fully exploited: more studies on additional triggers, tagging.

22. ATLAS-CMS22 Potential for Rare decays Before LHC B can be seen before LHC only if drastically enhanced. B K* will be measured but mass and angular distributions detailed enough to show New Physics only at LHC. A study proved good performance at nominal LHC luminosity. After 1 year 10 34 cm -2 s -1 3 years at 10 33 cm -2 s -1 B Will measure branching ration of Bs which is in SM of order Br < (10 -9 Perform high sensitivity search on Bd Different conclusions about BG: 1.CMS - already exploit isolation cuts in calorimetry 2. Different assumptions about tails in VTX resolution.

23. ATLAS-CMS23 Exclusive Rare decays of B mesons ATLAS statistics will allow angular analyses that can carry evidence for new physics. E.g. forward-backward asymmetry: SM MSSM C7 >0 MSSM C7 <0 Lowest mass region: sufficient accuracy to separate SM and MSSM if Wilson coefficient C7 <0 Three points: mean values of A FB in three q 2 /M B 2 experimental regions with error bars

24. ATLAS-CMS24 Undergoing physics studies not mentioned here: 1.Double heavy flavor mesons (b,c) 2.QCD tests of beauty production at LHC central region. Correlations bb. 3.Physics of Beauty baryons, production polarizations, decays. 4.Rare decays of b s gamma. 5.Rare decays of b other studies of ATLAS, CMS b-physics group

25. ATLAS-CMS25 ATLAS, CMS b-physics-related software 1.ATLAS, CMS – B-related online software under development: reconstruction Algorithms, trigger simulations. 2.ATLAS: offline MC simulation, reconstruction software, physics analyses software. Within a successful Data Chalenges-1 period 2002-2003 B-physics group studied B-performance for the Final version of detector layout. Data Chalenges-2 started 2004: grid production, Geant 4, databases, new Event Model 3.ATLAS, CMS: B-event Generators software For bb production we use Pythia tuned to Tevatron data. Herwig – we never tried. NLOQCD ( MNR code) does not give whole events. Installation of B-decays dedicated package EvtGen in common use and development with BaBar (main developer), LHCb, CDF, D0.

26. ATLAS-CMS26 B-physics prospects with ATLAS, CMS - conclusions 1.General purpose central LHC detectors are preparing a multi thematic B- physics program - including B-decays and B-production. 2.ATLAS, CMS B-physics trigger strategy rely on dimuon trigger for luminosity 2*1033 cm-2s-1 - extend selection menue at lower luminosities when there is spare processing capacity. 3.In CP violation the main emphasis will be on underlying mechanisms and evidence of New physics. ATLAS, CMS is especially precise in measurement of LHC gold-platted mode is also Bs J/ 4.Rare decays B have the most favorable experimental signature allowing to measure also at nominal LHC luminosity 10 34 cm -2 s -1. Will measure branching ration of Bs and sensitivity test for Bd. Precision measurements will be done for B K*. 5.Beauty production at central LHC collisions will be measured for QCD tests.