The LHC Heavy Flavour Programme

Transcription

1 The LHC Heavy Flavour Programme Tatsuya Nakada CERN and EPFL LHC Flavour Workshop , CERN 1

2 Contents 1) Introduction 2) LHC Experiments 3) Physics with 2008 data 4) Flavour Physics >2008 5) Conclusions Thanks to ATLAS(M. Smizanska), CMS (U. Langenegger) and LHCb colleagues. LHC Flavour Workshop , CERN 2

3 1) Introduction Goal of heavy flavour physics is now shifting from understanding of CKM paradigm (SM) to search for physics Beyond the Standard Model (BSM) appearing in loops. Following the past successes: e.g. charm from m(k 0 ), Br(K L µµ), etc. top from CPV, m(b 0 ), etc. before the c and t discoveries, look for signs of BSM in rare processes with b-hadrons. LHC Flavour Workshop , CERN 3

4 ALICE ATLAS CMS LHCb LHCf MOEDAL TOTEM 2) LHC Experiments Experiments being prepared now at LHC heavy ion and soft-pp experiment general purpose pp and heavy ion experiment general purpose pp and heavy ion experiment dedicated heavy flavour experiment forward 0 and production magnetic monopole search logs and diffraction physics ATLAS, CMS and LHCb are relevant for the flavour physics considered here, and I do not cover production and spectroscopy LHC Flavour Workshop , CERN 4

5 LHC LHCb/MOEDAL CMS/TOTEM ATLAS/LHCf ALICE LHC Flavour Workshop , CERN 5

6 dipole installation LHC Flavour Workshop , CERN 6

7 pt of B-hadron ATLAS/CMS ATLAS/CMS 100 µb LHCb LHCb 230 µb ATLAS Pixel LHCb RIH-2 CMS Tracker 1 Counts Invariant mass eta of B-hadron B π + π - d + - B d K π + - B s K K - B π + s K - Λ b p K - Λ b p π m( ) with no PID MeV/c Invariant mass Counts B π + d π B π - d K + - B s K K - B π + s K Λ b p K - Λ b p π 100 m( ) with PID (LHCb) GeV/c LHC Flavour Workshop , CERN 7

8 End of 2007: Engineering run very low s = 900 GeV detector commissioning, alignment and calibration Middle of 2008: Start of s = 14 TeV calibration and trigger commissioning, increasing luminosity toward for ATLAS/CMS and ~ for LHCb for physics From 2009: Stable physics s = 14 TeV ATLAS and CMS: clear interest to increase luminosities towards as quick as possible. B physics will become increasingly difficult. LHCb: collecting data with <10 33 for some years LHC Flavour Workshop , CERN 8

9 A possible scenario 2008 physics run for a period of 1/4 of the nominal year (10 7 sec) <L>=10 33 for ATLAS and CMS (optimistic?) <L>= for LHCb (should be possible ) Ldt = 2.5 fb 1 each for ATLAS and CMS (if <L> is lower, trigger could be adjusted to have a similar number of b s) Ldt = 0.5 fb 1 for LHCb ATLAS and CMS accumulate Ldt = 30 fb 1 each end of B physics era and move to regime (except B s µµ) LHCb collect Ldt >~ 10 fb 1 LHCb should have 10 fb 1 data by the end of 2013±1 LHC Flavour Workshop , CERN 9

10 3) Physics with 2008 data Very interesting results can be obtained for B s physics CP violation in B s J/ (i.e. s measurement) and Search for B s µµ decays where large, >O(1), BSM contribution not yet excluded Tevatron will run till 2009: CDF and D0, well understood detectors LHC can get b statistics fast, We need to organize ourselves for fast analysis LHC Flavour Workshop , CERN 10

11 Time dependent CP asymmetries in B s, B s J/ decays Final states with leptons: lepton trigger very effective for ATLAS, CMS and LHCb Flavour tag necessary opposite side: lepton, jet-charge and kaon same side: slow kaon from the fragmentation eff = tag (1 2w wrong ) 2 [10 2 ] O.S. S.S. combined e µ K Jet K ATLAS =4.56 CMS under investigation LHCb N.N. = 7.08 LHC Flavour Workshop , CERN 11

12 B s -B s oscillation has to be well resolved: good needed -good that m s is not too big -resolution function must be well understood measuring lifetimes, oscillation plot with D s etc. Proper time resolutions ATLAS CMS LHCb [fs] NB: worse resolution = more dilution in the CP asymmetries LHC Flavour Workshop , CERN 12

13 Good mass and vertex resolutions to reduce background B s mass resolutions and Background/Signal ratios ATLAS CMS LHCb m [MeV/c 2 ] 16.5 ) 14 ) 14 +) B/S ) with J/ mass constraint +) without mass constraint LHC Flavour Workshop , CERN 13

14 Event yields from the 2008 run Numbers of reconstructed J/ and those effectively flavour tagged ATLAS CMS LHCb N rec 23 k 27k 33 k N eff-tag rec 1.0 k? 2.3 k Full decay topology analysis is needed to determine J/ (CP = +1) / J/ (CP = 1) (L J/ - = 0, 2 vs L J/ - = 1) Total The background is assumed to be independent on tr. Should be measured from the side band data. CP-even CP-odd LHCb LHC Flavour Workshop , CERN 14

15 B s -B s oscillation phase and decay width difference with 2008 data ATLAS CMS LHCb ( s ) 0.158? ( s )/ s NB CP s s 1 s2 /2 less sensitive to s Standard model expectation: s = 0.04 LHCb: BSM effect down to the level of SM can be excluded/discovered with the 2008 data LHCb: J/, c, D s+ D s can be added and ( s ) = 0.01with L dt = 10 fb 1 data ATLAS and CMS: ( s ) 0.04 with L dt = 30 fb 1 data By ~2013, SM prediction of s tested to a level of ~5 LHC Flavour Workshop , CERN 15

16 Search for B s µ + µ decays Final states with leptons: lepton trigger very effective for ATLAS, CMS and LHCb Flavour tag not necessary, tough background PID: B, K, etc. vertex resolution: b µ X + b µ + X mass resolution: B µx, etc. + isolation, p T, etc. B s mass resolutions B s µ + µ ATLAS CMS LHCb m [MeV/c 2 ] LHC Flavour Workshop , CERN 16

17 With 2008 data ) assuming the SM Br = ~ ATLAS CMS LHCb uses distributions N ) signal ~2 ~2 for signal and background Limit at 90% CL N background ~5 ~ <~ (90%CL) LHCb; BSM contribution down to the level of SM can be excluded/discovered. SM prediction Expected CDF+D0 Limit Uncertainty in bkg prediction Integrated Luminosity (fb 1 ) LHCb: L dt = 10 fb 1, >5 observation for SM Br ATLAS and CMS: L dt = 30 fb 1, <~ (90%CL) (They plan to continue this programme at L=10 34, 4 in one year) LHC Flavour Workshop , CERN 17

18 4) Flavour physics >2008 Subjects which require very high statistics good control of systematics, detector and physics. Here are some examples Search for a BSM Lorentz structure in b s current using polarization of in b s+, for real or virtual B d K 0 µ + µ detailed studies of the event structure A FB : forward-backward asymmetry of µ + µ other angular distributions LHC Flavour Workshop , CERN 18

19 Final states with leptons: lepton trigger very effective for ATLAS, CMS and LHCb Flavour tag not necessary for one canonical year 10 fb (CMS study not yet available) 1 (ATLAS) and 2fb 1 (LHCb) ATLAS LHCb (m) [MeV/c 2 ] N signal ATLAS B/S <4.8 ~0.5 LHCb [MeV/c 2 ] m( 0 µµ) m( 0 µµ) [MeV/c 2 ] LHC Flavour Workshop , CERN 19

20 A FB performance ATLAS 30 fb 1 forward-backward asymmetry three canonical years LHCb 2 fb -1 one canonical year + ATLAS 30 fb -1 + Belle 2006 SM model SM extensions m µµ 2 [GeV 2 ] By ~2013, LHCb zero crossing point with 10 fb 1 (s 0 ) = 0.28 (GeV/c 2 ) 2 LHC Flavour Workshop , CERN 20

21 There is more information in K 0 µ + µ K 0 polarisation can be measured LHC Flavour Workshop , CERN 21

22 Examples for K 0 polarisation with 2fb 1 data NB: Theoretical complication: K *0 is a wide resonance Effect of non-resonant K to be better understood LHCb will look for other radiative decays, e.g. B s 47k events with 10 fb 1 LHC Flavour Workshop , CERN 22

23 An interesting quantity: R K With 10 fb 1 data K ± e + e 10 k K ± µ + µ 19 k LHCb by 2013 (R K ) = LHC Flavour Workshop , CERN 23

24 Extraction of Different ways to extract are considered by LHCb 1) Interfering b c+w ( us) and b u+w ( cs) a) via B s -B s oscillation time dependent decay asymmetries b) via DCS decays of D relative decay rates c) via D-D state mixing relative decay rates d) K 0 -K 0 state mixing Dalitz plot study 2) Interfering b u-tree+b d-penguins and B-B oscillations + U-spin time dependent decay asymmetries L0 hadron p T trigger, K/ identification: essential LHC Flavour Workshop , CERN 24

25 1-a) B s D s± K m and B s D m s K ± flavour tag, K/ identification (D s background), 1-b) B + DK + and B DK or B 0 DK 0 and B 0 DK 0 with D K ± m 1-c) B 0 DK 0 and B 0 DK 0 with D K ± mand D K + K, + 1-d) B + DK + and B DK or B 0 DK 0 and B 0 DK 0 with D K S + K/ identification and mass and vertex resolution to reduce combinatorial background Detector acceptance for charge asymmetry, kinematics, Description of D decays: strong phases between DCS and CA decay amplitudes, Dalitz plot distribution, Normalization of some background channels LHC Flavour Workshop , CERN 25

26 2) B d + and B s K + K flavour tag, K/ identification (K background), validity of U-spin symmetry (C) (S) CP asymmetries fit results corresponding to 2fb 1 B d + B s K + K B d K + B s + K (0.07*) (A CP ) (0.015*) (0.09*) LHCb performance in determination with 10 fb 1 D s K DK /KK ADS GLW+D Dalitz ( ) ) ~2013 LHCb tree determination of = 2.4, unaffected by BSM ) With a weak assumption on U-spin symmetry Could be affected by BSM LHC Flavour Workshop , CERN 26

27 Extraction of For LHCb, a promising method is time dependent Dalitz plot analysis for B d + 0 and B d + 0 : i.e. mode ( modes are marginal except 0 0 channel) LHCb B d fb 1 N signal B/S (m ) B d ( ) tag eff 14 k 1 60 MeV/c 2 50 fs 5.8% LHCb B d fb 1 N signal B/S (m ) B d ( ) 1200 <5 16 MeV/c 2 32 fs LHC Flavour Workshop , CERN 27

28 generated LHCb determination with mode with 2fb 1 data m 2 ( + 0 ) reconstructed m 2 ( 0 ) together with 0 0 mode, ~2013 LHCb determination of a with 10fb 1 ( ) = 4.6, could be affected by BSM LHC Flavour Workshop , CERN 28

29 BSM Phase of b s penguin Analogous to B d K S, time dependent CP asymmetry for B s can measure the BSM phase in b s penguin (for B s, with only t contribution, SM makes 0 CP asymmetry) LHCb B s performance with 2 fb 1 data (m B s ) B/S N sig ) ( ) ( s-eff ) 12 MeV/c fs 0.1 ) Br = angular analysis needed to resolve CP=1 and = 1 states ~2013 with 10 fb 1 data: ( s-eff ) = 0.04 (B d K s for LHCb, ( d-eff ) = 0.14) currently ( d-eff ) = 0.18 LHC Flavour Workshop , CERN 29

30 BSM in the D system LHCb will collect a large D tagged D 0 sample (also used for PID calibration) D 0 K + K + K + K + N signal [10 6 ] Combined with slow + to make D + Use B D + ± X to determine D + vertex 45k K + decays/2 fb 1, B/S~2.6, ( D )=45 fs ~2013 LHCb performance with 10 fb 1 data (x' 2 ) = , (y') = ±0.37 ± CP performance under study (KK and ) BABAR BELLE LHC Flavour Workshop , CERN 30

31 Other topics Lepton favour violating decays 3µ, µee? Lepton flavour violating B decays B eµ Lepton flavour violating D decays D eµ being or will be looked at. (we cannot do everything now) LHC Flavour Workshop , CERN 31

32 5) Conclusions i) LHC is a b-factory coming online soon, experiments are busy to be ready. ii) Physics with s = 14 TeV will start in data could allow us to exclude/discover BSM effect in the B s sector down to the SM level e.g. for B s J/ and B s µµ. iii) By 2013, wide range of flavour physics in B and D will be explored by LHCb extending further the results obtained by BABAR, BELLE, CDF and D0. iv) We need help from theory. With a much better theoretical understanding for the form factors and decay constants, we might already see a deviation from CKM with, V ub, m d, and sin2. LHC Flavour Workshop , CERN 32

33 LHC experiments will soon face the reality. There will be some bad surprises; background level is higher than expected, resolution is worse, etc But with real data, we can learn how to cope with them. LHC Flavour Workshop , CERN 33

34 LHC experiments will soon face the reality. There will be some bad surprises; background level is higher than expected, resolution is worse, etc But with real data, we can learn how to cope with them. CESAR, DORIS, LEP, Tevatron, PEP-II and KEKB, all produced flavour physics results beyond the original expectations. There must be good surprises at LHC too! LHC Flavour Workshop , CERN 34

35 My scenario matrix for 2014 at LHC ATLAS CMS high p T physics BSM Only SM BSM LHCb flavour physics Only SM BSM BSM Particle Physics Exciting moment is ahead! LHC Flavour Workshop , CERN 35