Flavour physics at the LHC Marie-Hélène Schune LAL-Orsay IN2P3 Introduction (Very) rare B decays Precise measurements of UT angles And also Bc and D physics I will not discuss b production physics Many thanks to Maria Smizanska (ATLAS), Urs langenegger (CMS) and my LHCb colleagues Vth SuperB workshop, Paris May 9-11

ATLAS, CMS, LHCb and the LHC The LHC : proton-proton collisions at √s = 14 TeV in a 27km ring Design luminosity from L=1033cm-2s-1 (2008) to 1034cm-2s-1 for ATLAS and CMS Two general purpose detectors : ATLAS and CMS One experiment dedicated to flavour physics : LHCb LHCb ATLAS pT of B hadron CMS Rapidity of B hadron Vth SuperB workshop, Paris May 9-11

ATLAS and CMS main features Both detectors are designed for high pT (=discovery) physics Charm and B events are mostly low pT events  triggering is challenging  use mostly decay modes with µ High trigger efficiency for µ Dedicated B trigger for both experiments Good tracking and calorimetry (but no K/p separation) CMS : PWO crystals for the calorimeter ATLAS : pixel detector  CP violation rare B decays (search for new physics) Bs oscillation Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 LHCb main features Forward one-arm spectrometer (10 to 300 mrad) Very precise vertex reconstruction and powerful PID Experiment dedicated to B physics  wider trigger VELO Collision point Very high trigger efficiency on  channels High trigger efficiency on γ, e and hadron channels 40 MHz  1MHz (hardware)  2 kHz (software) Output rate Trigger Type Physics Use 200 Hz Exclusive B candidates Specific final states 600 Hz High Mass di-muons J/, bJ/X 300 Hz D* Candidates Charm, calibrations 900 Hz Inclusive b (e.g. bµ) B data mining 2 kHz Vth SuperB workshop, Paris May 9-11

(Integrated) luminosities LHC machine, pp collisions at s = 14 TeV (bunch crossing : 40 MHz) design luminosity : L = 1034 cm–2s–1 average non-empty bunch crossing rate : f = 30 MHz (in LHCb) Pileup: n = number of inelastic pp interactions occurring in the same bunch crossing Poisson distribution with mean <n> = Linel/f, with inel = 80 mb for LHCb <n> = 25 at 1034 cm–2s–1  problematic for B physics At LHCb: L tuneable by adjusting final beam focusing Run at <L> ~ 21032 cm–2s–1 (max. 51032 cm–2s–1) Clean environment: <n> = 0.5 Less radiation damage 2 fb–1 of data in 107 s (= nominal year) ATLAS or CMS : a nominal year is 10 fb-1 pp interactions/crossing LHCb n=0 n=1 Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 A scenario Hopefully in 2008 : ∫Ldt = 0.5 fb-1 for LHCb ∫Ldt = 2.5 fb-1 each for ATLAS and CMS 2009-2011 : ∫Ldt = 30 fb-1 each for ATLAS and CMS Progressive end of the “low” luminosity running. end of B physics era (except Bsμμ) and move to 1034 regime In ~2013 LHCb should have collected ~10 fb-1 (= 5 nominal years) For B physics (except Bsμμ) consider : 30 fb-1 for ATLAS and CMS 10 fb-1 for LHCb Vth SuperB workshop, Paris May 9-11

Flavour physics framework Today : the SM is in reasonably good shape Good agreement between sides and angles measurements  New physics should appear as a correction The Bs sector is less tested A second UT has to be considered c η0  CP violation through the CKM mechanism (ρ,η)SM given by tree processes   measurement should be improved Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 New Physics Penguin diagram ? Box diagram d vs Cd Model independent NP parameterization in mixing : SM s vs Cs 5 new free parameters Cs,s Bs mixing Cd, d Bd mixing CeK K mixing SM Vth SuperB workshop, Paris May 9-11

 Measurements to be done “Control” measurements Bs oscillations sin(2β) from Bd J/ΨKs Measure processes very suppressed in SM CP in Bs mixing ( in SM) from BsJ/f Radiative and very rare B decays BdK*g, Bs f g, Bd K*mm, Bs mm Precision measurements of UT angles Compare pure tree level processes with processes sensitive to NP : bsss penguin decays Compare angles and sides measurements And also … Bc, D measurements Any inconsistency will be evidence for NP Requires clean and improved theory predictions Vth SuperB workshop, Paris May 9-11

“Control” measurements Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Tagging principle Luis Fernández What is different from B factories ? + information from Brec side (“same-side”)  better Bs tagging than Bd tagging - b b correlation instead of B B correlation  intrinsic dilution (wtag = 50% in case of Bs production in the opposite side …) Effective tagging efficiency eff=(1-2)2 = 6 to 10 % (~30% at B factories) and also correlation between tagging category and trigger Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 sin(2β) from BdJ/Ks Current measurement (B-factories) : sin(2β) = 0.668 ± 0.026 Expected uncertainty at the end of BABAR+BELLE data taking: ~ 0.018 Expected to be one of the first CP measurements: Validation channel for CP analyses (in particular tagging control) : can be used from 0.5 fb-1 ATLAS LHCb s(sin(2β)) 0.01 (30fb-1) 0.02 (2fb-1) 2fb-1 Expect 0.01 for 10fb-1 Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bs mixing frequency Measurement of ms: CDF observed Bs oscillations in 2006 : ms=17.77 ± 0.10 ± 0.07 ps–1 compatible with the SM expectation ATLAS (10fb-1) LHCb (2 fb-1) s(t)[fs] ~110 40 s(M(Bs))[MeV] 43 14 N(Dsp) 2.7k 120k B/S <1 0.4 stat(ms) = ± 0.007 ps1, i.e. 0.04% will be completely dominated by ssyst on proper time scale (~ 0.5% ? using tB ?) interesting physics result AND a proof that - the tagging of the B production state can be controlled - a precise proper time measurement can be performed in the LHC environment Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 (Very) Rare B decays Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 fs and DGs from BsJ/ Tagging and decay time reconstruction necessary Good mass resolution and good proper time reconstruction  low background J/ final state contains two vectors : Mixture of CP-even and CP-odd components CP=+1 for L =0,2 and CP=-1 for L=1 Angular analysis needed to separate them Total CP=+1 Bkgd (to be checked on data (SB)) CP=-1 cos qtr Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 ATLAS CMS LHCb s(t)[fs] 83 77 36 s(M(Bs))[MeV] 16.5 14 N(evts) 106k 109k 131k B/S 0.30 0.33 0.12 s(DGs/Gs) 0.03 0.015 0.0092 s(fs) 0.08 0.072 0.023 ~0.04 (30fb-1) ~0.01 (10fb-1) Untagged fit : if ΔΓs0 still sensitive to fs (+ no need to resolve for Dms) Results for one nominal year at low luminosity Adding pure CP states: J/yh, hcf, DsDs  s(fs)= 0.021 With the full B physics ∫Ldt (10fb-1 for LHCb and 30fb-1 for ATLAS and CMS) : test up to 4-5s fs well known from indirect UT fits: -0.037±0.002 After one year of nominal data taking : test up to 2s Vth SuperB workshop, Paris May 9-11

Example of the impact of fs from BsJ/ End of LHC σ(s)~0.6° ? Present knowledge on fs Expected precision at the end of Tevatron σ(s)~5.6° ! the x scales are different ! Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 BK* and Bs ? A priori sensitive to New Physics But measured BR (BK* ) in agreement with SM with a precision better than few % However Bs not seen and still room for improvement in ACP ATLAS (30fb-1) LHCb (2fb-1) s(MB) 65 MeV s(Proper time) 62 fs Yield K*g 14.1k 35k B/S (90%CL) K*g <100 <0.7 Yield fg 4.7k 9k B/S (90%CL) fg <400 <2.4 End of B factories (2 ab-1) N(K*g) ~13k Fully dominated by MC stats. Should be better. Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 BK*ℓℓ Second order diagram  sensitive to New Physics Well known SM inclusive branching fraction : ~10-6 Sensitive probe to NP : Forward-backward asymmetry AFB Goto et al hep-ph/9609512 AFB ℓℓ CM frame ℓ+ ℓ- q B s0 value sensitive to NP End of BABAR+ BELLE data taking : s0 known to ~25% Vth SuperB workshop, Paris May 9-11 s = (m)2 [GeV2]

Vth SuperB workshop, Paris May 9-11 AFB(s), fast MC, 2 fb–1 s = (m)2 [GeV2] ATLAS LHCb s(M(Bd)) [MeV] 39 14 N(signal) 2500 7700 B/S <4 0.4  0.1 NB : non resonant contribution below the K* peak is ignored 30 fb-1 2 fb-1 LHCb with 10 fb-1 zero of AFB(s) located to ±0.28 GeV2 (~7%) Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bs  +– Very rare loop decay, sensitive to new physics: BR ~3.510–9 in SM can be strongly enhanced in SUSY (up to x100) Current 90% CL limit from CDF+D0 with 1 fb–1 is ~20 times SM + : pure leptonic channel (trigger very effective) + : no need for tagging + : no need for decay time measurement - : very tough background (dominated by b, b) but size of MC samples limited  Impact parameter cuts, PID ... ATLAS CMS LHCb s(M(Bs)) MeV 70 36 18 N(Background) 20 20 13.8 +22.0 -13.8 N(Signal) for the SM BR 7 6.10.1 Use of the shapes of discriminating variables for signal and background 10 fb-1 Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bs  +– LHCb limit on BR at 90% CL BR (x10–9) Uncertainty in bkg prediction Expected final CDF+D0 limit SM prediction Integrated luminosity (fb–1) Excluded BR(Bs  +–) in 10-9 ATLAS 6.6 (30 fb-1) CMS 14 (10 fb-1) LHCb 3.5 (0.5 fb-1) LHCb with 2 fb–1 : 3 evidence of SM signal LHCb with 10 fb–1 : 5 evidence of SM signal ATLAS and CMS running at 1034 cm-2s-1 4 evidence of SM signal in one year Vth SuperB workshop, Paris May 9-11

Precise measurements of UT angles Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 g measurements Unique to LHC u s c s BsDsK decay mode : interference via Bs mixing Similar to B factories D0 Kp, K3p (ADS) D0 KK, pp (GLW) D0 Kspp (GGSZ) A(B-D0 K-) = AB A(B-D0 K-) = ABrB e i(d-g) Need LHC data  from B and BsKK Time dependent CP asymmetries + U-spin symmetry Sensitive to NP Crucial ingredients : L0 hadron pT trigger, K/p separation Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 g from Bs  DsK Depends on s +  Similar to 2+ extraction with B0  D*, but the two decay amplitudes are similar (~3)  their ratio can be extracted from data m = 14 MeV/c2 Expect 6200 signal events/year B/S <0.5 at 90% CL Bs  Ds–+ background (with ~ 12  larger BR) suppressed using PID:  residual contamination estimated to 155% Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Fit the 4 tagged time-dependent rates: Extract s + , strong phase difference , amplitude ratio Bs Ds also used in the fit to constrain other parameters (mistag rate, ms, s …) Both DsK asymmetries 10 fb–1, ms = 20 ps–1) Ds–K+: info on  + ( + s) Ds+K–: info on  – ( + s) s(g) ~ 13 with 2 fb–1 expected to be statistically limited Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11  from B±  DK± Interference between the two diagrams if same final state A(B-D0 K-) = AB A(B-D0 K-) = ABrB e i(d-g) D0  K or K3 (“ADS”) strategy depends on : rB, g , d the relative magnitudes (known) and strong phases between the D0 Cabbibo-allowed and Cabbibo-suppressed decays D0  KK or  (“GLW”) strategy depends on : rB, g , d  common ADS +GLW fit can solve for all unknowns, including  Decay 2 fb–1 yield Bbb/S B–  (K–+)D K– 28k ~0.6 B+  (K+–)D K+ B–  (K+–)D K– 180 4.3 B+  (K–+)D K+ 530 1.5 rB=0.077 Sensitivity with 2 fb-1 σ(γ) ~ 5°-15° (depends on strong phase δD) Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11  from B0  DK*0 ds colour-suppressed colour-suppressed Despite the presence of a B0 : self-tagging mode Magnitude ratio = rB ~ 0.4 Treat with same “ADS+GLW” method Modes : D0  Kp, KK, pp Decay mode (+cc) 2 fb–1 yield Bbb/S B0  (K+–)D K*0 3400 <0.3 B0  (K–+)D K*0 500 <1.7 B0  (K+K–, +–)D K*0 600 <1.4 rB=0.4 Sensitivity with 2 fb-1 σ(γ) ~ 7°-10° (depends on strong phase δD) Vth SuperB workshop, Paris May 9-11

 from B and BsKK Measure CP asymmetry in each mode: Adir and Amix depend on mixing phase, angle , and ratio of penguin to tree amplitudes = d ei Exploit U-spin symmetry (Fleischer): Assume d=dKK and =KK 4 measurements and 3 unknowns (taking mixing phases from other modes)  can solve for  With 2 fb–1: 36k B, B/S ~ 0.54 36k BsKK, B/S < 0.14 Sensitivity to Adir and Amix ~ twice better than current world average With PID KK invariant mass  invariant mass With PID stat() = 4 If perfect U-spin symmetry assumed stat() = 7-10 + fake solution If 20% violation of U-spin symmetry For 2 fb–1 : Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 g measurement summary B mode D mode Method s(g), 2 fb–1 B+ DK+ Kp + KK/pp + K3p ADS+GLW 5º–15º B+  DK+ KSpp Dalitz 8º(*) KKpp 4-body “Dalitz” 15º(*) B0  DK*0 Kp + KK + pp 7º–10º Bs  DsK KKp tagged, A(t) 13º Bd  + Bs KK A(t) + U-spin 4º (perfect U-spin) 7º–10º (20% U-spin viol.) (*) Signal only, no accept. effect Could be affected by NP s(g) with 2fb-1 Under study : B+  D*K+ ADS+GLW B+  DK+ Kppp 4-body “Dalitz” B0  DK*0 GGSZ B  DK + Bs  DsK Bd  + Bs KK 4-5º 4º (perfect U-spin) 7º–10º (20% U-spin viol.) With 10 fb-1 obtained from DK and DsK channels s(g) should be ~ 2-3º Vth SuperB workshop, Paris May 9-11

a sensitivity with B00 00 –+ +– Challenging analysis in the LHC environment : Need for 0 reconstruction ep0 =53 % for B0p+p-p0. Time dependent Dalitz plot analysis. average gen 70 expts superimposed (2fb–1) 2 vs  2fb-1 : 14k signal events B/S<0.8 @ 90%CL. (time resolution : 50 fs, tagging power : 6%) Use B/S=1 for sensitivity studies 15% fake solutions (< 1% with 10 fb–1) stat() < 10º in 90% of the cases (2 fb–1) Vth SuperB workshop, Paris May 9-11

bsss hadronic penguin decays Bd / Bs Tree Bd / Bs Penguin f Ks / f Vtb Vts* d/ s ? d/ s d/ s Vcb Vcs* Ks / f J/y Same s-penguin diagram contributes to Bd and Bs sin(2β) from J/ΨKs Using bsss naïve average Currently: DS=sin(2β)Tree-sin(2β)Peng is 2.6s away from 0 2 fb–1 yield B/S Bd  Ks 0.8k <2.4 @ 90%CL Bs    (BR=1.410–5) 4k 0.4 < B/S < 2.1 @ 90%CL Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 The Bs decays are PVV decays  full angular, time-dependent CP analysis M(ff) GeV 34M bb events … Bs mass resolution : 12 MeV Proper time resolution : 42 fs Bs    CP violation <1% in SM  significant CP-violating phase NP would be due to New Physics 2fb-1 10fb-1 Bd  Ks s(sin2beff) 0.32 0.14 Bs    s(fNP) rad 0.10 0.042 Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bc and D physics Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bc meson properties Studying Bc can help understanding heavy quark dynamics • Different theoretical descriptions give Bc properties with large uncertainties Bc  J/ψp 1 fb-1 The mass and lifetime measurements could be done with a small data sample. 1 fb-1 2 fb-1 CMS LHCb Bc mass resolution [MeV] 22.0 (stat) 14.9 (syst) ~14 N(signal) 120 14000 s(ct)/ct ~10% ~ 6% PDG 2006 : J/y ℓ n s(ct)/ct ~ 37 % Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Charm physics Dedicated D* trigger  huge sample of D0h+h– decays (100M / 2fb-1) Useful for PID calibration CP violation and mixing in D0 decays (tag D0 or anti-D0 flavour with charge of pion from D*D0) Use BD*hX to find the D* vertex 2fb-1 D0 K-p+ K+K- p+ p- K+p- N 50M 5M 2M 0.2M D* from B decays Interesting (sensitive to NP) & promising searches/measurements: Time-dependent D0 mixing with wrong-sign D0K+– decays Direct CP violation in D0K+K– ACP  10–3 in SM, up to 1% (~current limit) with New Physics Expect stat(ACP) ~ O(10–3) with 2 fb–1 LHCb (10fb-1) s(x’2)~0.06 10-3 s(y’)~0.7 10-3 End of B factories (2ab-1) s(x’2)~.1-.2 10-3 s (y’)~2-3 10-3 Performances studies just started : not as detailed as in B physics case Vth SuperB workshop, Paris May 9-11

Impact on Unitarity Triangle Taken from V. Vagnoni at CKM06-Nagoya Without LHCb With LHCb at 10 fb-1 But hopefully some NP will show up … Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Conclusion Data taking for physics will start in 2008 at √s = 14 TeV and experiments are getting ready Search for New Physics will be possible through several observables : Bs  +–, BsJ/, radiative decays … With the full B dataset CKM matrix elements will be very well measured B and D physics exploration will continue after B factories and Tevatron But in order to translate very precise measurements of experimental quantities to very precise SM parameters determination one needs improved theoretical computation of hadronic parameters (form factors, decay constants …) What I have shown is based on (very detailed) MC simulations ; reality will be different (higher backgrounds, worse resolution …) and it will take some time to understand the detectors. Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Backup slides Vth SuperB workshop, Paris May 9-11

Framework : the CKM matrix Mass eigenstates  weak interaction eigenstates  mixing matrix : the Cabbibo-Kobayashi-Maskawa matrix Weak interaction eigenstates Mass eigenstates CKM matrix Transition amplitude between the quarks i and j : Vij Vud Vus Vub Vcd Vcs Vcb Vtd Vts Vtb d’ s’ b’ = d s b W b u Vub Vij complex  CP violation Wolfenstein parametrisation 1-2  A 3(-i) - 1- 2/2 A 2 A3(1- -i) -A 2 1 + O(4) Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 LHCb trigger Vth SuperB workshop, Paris May 9-11

Tagging is needed for many CPV measurements We need to know the flavour of the B at a reference t=0 (at the primary vertex) Tag (give best estimate of) the flavour by examining the rest of the event Dz/bgc = Dt Bs0 rec t =0 b s u K+ Dt picoseconds after leaving the primary vertex, the reconstructed B decays. PV b-hadron l + (e+, m+) l - (e-, m-) K - Uses flavour conservation in the hadronization around the Brec eD2  1% (B0) , 3% (Bs) Same-side tag Assume: Opposite side tag eD2  5% Vth SuperB workshop, Paris May 9-11

Tagging performances for ATLAS, CMS and LHCb eD2=e(1–2w)2 Tag LHCb ATLAS CMS Opposite  0.7% Opposite e 0.5% 0.3% Opposite K 1.6% - Opposite Qvtx 1.0% 3.6% Same side  (B0) 0.8% Same side K (Bs) 2.7% Combined (B0) 4%–5% 4.6% Combined (Bs) 7%–9% Vth SuperB workshop, Paris May 9-11

Vth SuperB workshop, Paris May 9-11 Bs-> Psi Phi L(t, qtr) = (1-RT) Leven(t) (1+cos2qtr) / 2 + RT Lodd(t) (1-cos2qtr) Vth SuperB workshop, Paris May 9-11

 from B and BsKK Measure CP asymmetry in each mode: Adir and Amix depend on mixing phase, angle , and ratio of penguin to tree amplitudes = d ei Exploit U-spin symmetry (Fleischer): Assume d=dKK and =KK 4 measurements and 3 unknowns (taking mixing phases from other modes)  can solve for   2 fb–1 stat() = 4 If perfect U-spin symmetry assumed 2 fb–1 If 0.8<dKK/d<1.2 assumed stat() = 7–10 + fake solution Vth SuperB workshop, Paris May 9-11

a sensitivity with B00 sM ~ 10 MeV/c2 sM ~ 15 MeV/c2 2fb-1 : 14k signal events B/S<0.8 @ 90%CL. Use B/S=1 for sensitivity studies merged resolved <>=53% Distribution of fit error 15% (< 1%) fake solutions with 2 (10) fb–1 Vth SuperB workshop, Paris May 9-11 stat() < 10º in 90% of the cases (2 fb–1)

SU(2) analysis of B0  +–, ±0,00 Larger branching fraction than pp Small BF(B0r0r0) (= 1.20.40.3 10-6) Low penguin contamination  good limit on a-aeff VV final state  3 polarization amplitudes In principle: dilution due to mixed CP In practice: dominated by longitudinal polarization  pure CP-even state B0  +–, ±0 measurements are not competitive with B-factories Main LHCb contribution could be B0  00 (time dependent analysis) : with 2fb-1 1k events reconstructed Vth SuperB workshop, Paris May 9-11