B Physics prospects at LHC Rencontres de Moriond “Electroweak Interactions and Unified Theories” 5-12 March 2005 B Physics prospects at LHC Marta Calvi Università di Milano Bicocca and INFN Electroweak Interactions and Unified Theories, 2005

B Physics in the LHC era At LHC start-up several precise measurements will be available from B-Factories and Tevatron to test the CKM paradigm of flavour structure and CP violation. (from CKM-fitter ) However New Physics could still be hidden in mixing, in box and in penguin diagrams, realm of indirect discoveries. If NP will be found at LHC in direct searches, B Physics measurements will allow to understand its nature and flavour structure. Electroweak Interactions and Unified Theories, 2005

A complete program on B Physics would include: Precise measurement of B0s-B0s mixing: Dms, DGs and phase fs. BsDsp, … BsJ/yf, BsJ/yh(’) Precise g determinations including from processes only at tree-level, in order to disentangle possible NP contributions Several other measurements of CP phases in different channels for over-constraining the Unitarity Triangles BsDsK, B0D0K*0, B0pp&BsKK, … B0fKs, Bsff, ... B0rp, B0rr, … Search for effects of NP appearing in rare exclusive and inclusive B decays B0K*g, B0K*0l+l-, bsl+l-, Bsm+m-... Electroweak Interactions and Unified Theories, 2005

Advantages of hadron colliders Huge bb cross section: sbb~500 mb @14 TeV (~1nb @Y(4S) ) Access to all b-hadrons: Bd,Bu, Bs, b-baryons and Bc The challenge Presence of underlying event. High particle multiplicity. High rate of background events (sinel~80 mb). Experimental requirements Trigger (also on fully hadronic decays) Excellent tracking and vertexing (mass resolution, proper time resol.) Excellent PID Other B physics topics at LHC: b production, bb correlation b-baryon physics, polarization Bc physics Electroweak Interactions and Unified Theories, 2005

LHC: pp at s =14 TeV, nbco=40 MHz ATLAS/CMS: for discovery Physics central detectors: |h| < 2.5 run at maximum available luminosity ℒ (cm–2s-1)= 21033 / 1034 ~ 1013 bb produced per year (1yr=107s) Npp/bc ~ 4 / 23 B-physics program will depend on trigger strategy LHCb: dedicated to B Physics forward spectrometer: 1.9 < |h| < 4.9 run at lower luminosity (locally defocusing) ℒ (cm–2s-1) = 21032 1012 bb produced per year Npp/bc ~ 0.4 bb correlation qb qb Electroweak Interactions and Unified Theories, 2005

LHCb trigger 40 MHz Level-0: high pT (m,e,g,h) + pile-up system Hardware trigger [4 ms] L0 efficiency L1 efficiency L0*L1 eff. 1 MHz Level-1: high IP, high pT tracks Software trigger [1 ms] 40 kHz HLT: software trigger on complete event [10 ms] 200 Hz + 1.8 kHz HLT rate Event type Calibration Physics 200 Hz Exclusive B candidates Tagging B (core program) 600 Hz High mass di-muons Tracking J/, bJ/X (unbiased) 300 Hz D* candidates PID Charm (mixing&CPV) 900 Hz Inclusive b (e.g. bm) Trigger B (data mining) Systematics from data Electroweak Interactions and Unified Theories, 2005

CMS trigger 50kHz at start up in 2007 Level-1 Trigger designed to cover widest possible range of discovery Physics (Higgs, SUSY ...) B Physics events triggered by single m or 2m triggers. Only a small fraction of HLT output accounted for inclusive b,c (~5Hz 1m) 100 Hz Exclusive B events selected at HLT exploiting online tracking To stay within time budget (~40 ms/evt) restrict Bs reconstruction to Region of Interest around the m, or use reduced # hits/track (Dsp ) s(pT) e.g. BsJ/yf Lvl-1 e HLT e events 10 fb-1 Trigger rate 16.5% 11.9% 84 k <1.7 Hz full tracker Electroweak Interactions and Unified Theories, 2005

ATLAS trigger Three level Trigger: 40 MHz  Level-1(75 kHz)  Level-2 (2 kHz)  Event Filter(200 Hz) B-physics ‘classical’ scenario: LVL1 muon with pT>6 GeV/c, ||<2.4, LVL2 muon confirmation, ID track ‘full scan’ Flexible trigger strategy to maximize B-physics capabilities at ℒ =2 1033 cm-2s-1 and with reduced detector at start-up: Start with a di-muon trigger Add further triggers in the beam-coast and for low-luminosity fills. Additional triggers will require a single m at LVL1 and a Jet or em. cluster. LVL1 will guide reconstruction at LVL2 and LVL2 will seed EF. Electroweak Interactions and Unified Theories, 2005

B0s-B0s mixing with Bs0  Dsp Bs0Ds-p+ (Ds-fp-, fK+K- ) Expected unmixed Bs Ds sample in one year of LHCb data taking LHCb: 80k events/yr B/S=0.32 st~ 40 fs 5 observation of B0s-B0s oscillation up to Dms=68 ps-1 1 yr Once observed, precision to measure Dms is ~0.01ps-1 proper time resolution (fs) ATLAS/CMS Events triggered by m from opposite b decay. Performance strongly dependent on the allocated bandwidth. ATLAS: (LVL1 pTm > 6 GeV/c) in 10 fb-1 expect. sensitivity up to Dms=36 ps-1 CMS: (restricting to 5 Hz at HLT) in 20 fb-1 expect. sensitivity up to Dms=20 ps-1 Electroweak Interactions and Unified Theories, 2005

fs and Gs with BsJ/f (h) The “gold plated” decay of Bs, sensitive to the weak phase of Vts SM: fs =-22 ~ -0.04  High sensitivity to NP in Bsmixing BsJ/f is a complicated analysis: 2 CP even, 1 CP odd contributing amplitudes  fit angular distribution of decay states as function of proper time. Derive also DGs=G(BsL)-G(BsH) ( DGs/GsSM ~0.1 ) BsJ/f s(sinfs) s(DGs/Gs ) ℒ LHCb ~0.06 0.018 2 fb-1 ATLAS ~0.04 0.012 30 fb-1 CMS ~0.03 0.015 30 fb-1 If Dms~20 ps-1 Similar sensitivity reached in LHCb also using BsJ/y()h, Bshc(4h)f with 7k+3k events/yr, under study. Electroweak Interactions and Unified Theories, 2005

Time dependent BsBs asymmetries  from BsDsK Measure   fs from 4 time-dependent rates: BsDsK and BsDsK (+CP conjugates) Use fs from BsJ/ f Only tree diagrams  g insensitive to NP in mixing BsDsK BsDs Time dependent BsBs asymmetries Need excellent PID for K/p separ. 5400 events/ yr B/S<1.0 at 90% CL () =14º (1 year) 5 yrs of data, ms= 20 ps -1 20<<20 New analysis underway: combination of BsDs(*)K and B0D(*)p using U-spin symmetry. Expected sensitivity ~5º in 5 year. Electroweak Interactions and Unified Theories, 2005

 from B DK*, DCPK* (—–) Theoretically clean determination of g. Measure 6 time-integrated decay rates with B0D0K*0 self-tagged through K*0K+p- and DCPK+K-(or p+p-) A1 = A1 A3 A4 A2 2    Dunietz variant of the Gronau-Wyler method: A(BDCPK*)=1/2 (A(BD0K*) + A(BD0K*)) A3 /2 = 1/2 ( |A1| + |A2| ei (+) ) Similar to B± D0K± but here two colour suppressed diagrams and |A2|/|A1|~0.4 Variant of the Gronau-Wyler method as proposed bt I.Dunietz: Amplitude triangles are not as squashed as in case of B+/- -> DK+/- Difficulty: also detect the D0 CP eignestate Dcp LHCb 1 year yield B/S B0 D0 (K+) K*0(K+) 3000 <0.6 B0 DCP(K+K-)K*0(K+) 540 <2.9 ()=7º8º (1 year) for 55 <  < 105 deg 20 <  < 20 deg Electroweak Interactions and Unified Theories, 2005

 from B and BsKK Bd/s /K /K Bd/s Large penguins contributions in both decays Measure time-dependent CP asymmetry for B and BsKK and exploit U-spin flavour symmetry for P/T ratio (R. Fleischer). Use RICH detectors for K/p separ. without RICH Bd+- Take fs, fd from J/,J/Ks  can solve for g B (95%CL) d sM=17 MeV BsKK (95%CL) events/yr B/S B 26 k <0.7 BK+ 135 k 0.16 BsKK 37 k 0.31 () = 4º6º (1 year) g (º) +(theory) Electroweak Interactions and Unified Theories, 2005

r+- a from B r-+  +p- r00 Quinn & Snyder: time dependent analysis of Dalitz distribution allows a clean determination of a independently from penguin contributions M(p0p-) M(p0p+) po reconstr. eff. 11-par. fit including resonant and non-res. background sa vs B/S Merged po sright Resolved po sleft LHCb: 10800 evts/yr B/S<3 sa < 10o (1 year) Electroweak Interactions and Unified Theories, 2005

B0  K*0 +- BR(B0K*+-)SM=(1.20.4)x10-6 ACPSM < 0.05% BR(s) AFB(s) BR(B0K*+-)SM=(1.20.4)x10-6 ACPSM < 0.05% Zero of AFB(s) known in SM at 5% Sensitivity to NP via non-standard values of Wilson coeff. C7,C9,C10 s=M(+-)2 [GeV2] (s)/s(%) (AFB) LHCb: 4400 evts/yr B/S<2.6 (BR) ~ 2% (ACP) ~ 2% Sensitivity to AFB need careful study of background shape. In 5 years: (AFB )~ 0.12, fitting the intersection at zero: (s0 ) ~ 0.02 ATLAS ~2000 events, B/S=0.14 (30 fb-1) Electroweak Interactions and Unified Theories, 2005

Bs0  +- BR(Bs0+-)SM = (3.50.1)x10-9 Good sensitivity to NP BR(Bs0+-) ~(tanb)6, ACP ~(tanb)3 for large tanb Bs  m+m- CMSHLT CMS Lvl-1 e HLT e events Bs+- Trigger rate offline evts offline backgr 15.2% 33.5% 47 <1.7 Hz 7 <1 10 fb-1 s=74 MeV Bs0+- Bd0+- backgr. 1 year 1033cm–2s-1 9 1 31 1 year 1034cm–2s-1 92 14 660 ATLAS CMS Full tracking LHCb: 1 year 17 events Bs0+- Backgr. study requires additional MC statistics, present limit from bmX+cc. B/S<5.7 (MBs)=18 MeV/c2 s=46 MeV Bs mass resolution SM signal in the first year ! Electroweak Interactions and Unified Theories, 2005

Conclusions Future experiments at LHC will offer a great opportunity to pursue an extensive program on B Physics Access to B0 and Bs decays with high statistics will allow precise determination of: B0s-B0s mixing parameters Dms, DGs and fs a,b,g measurements in several channels access to rare decays over-constrain the Unitarity Triangles and look for signals of NP The program will also include studies with b-baryons and Bc mesons. The goal will be reached thanks to: dedicated triggers excellent mass and decay-time resolution excellent particle identification capability Electroweak Interactions and Unified Theories, 2005