Search for Physics Beyond the Standard Model at B Factories

Transcription

1 Search for Physics Beyond the Standard Model at B Factories Gautier Hamel de Monchenault CEA-Saclay DAPNIA/SPP on behalf of the BABAR & BELLE Collaborations Moskow, 29 July 2006

2 New Physics in Flavor Sector 2006 CKM fit (relatively) good agreement of experimental data with Standard Model predictions unprecedented test of the flavor sector of the theory Models of New Physics must satisfy SM-like flavor structure at low energy no right-handed couplings small quark mixing only one source of CP violation (CKM) Summary of CKM constraints (pre-ichep06) New sources of flavor or CP violation can induce subtle deviations from Standard Model predictions For instance, in MSSM 124 independent parameters 44 are CP violating

3 NP Strategy at B Factories M.Hazumi plenary R.Barlow plenary Improve CP asymmetry measurements in tree-dominated decays Search for differences in CP asymmetries between tree- and penguin- dominated processes Look for deviations from Standard Model Flavor Mixing large deviations in Bd system are unlikely but SUSY can affect mixing in the Bs system distinguish measurements involving flavor mixing or not FCNC in B-meson decays helicity-conserving helicity-changing examples of SUSY diagrams with intermediate squarks and gluinos FCNC in charm decays Very rare B decays (e.g. leptonic) Lepton Flavor Violating processes (not covered in this talk)

4 Theoretical Tool: the Operator Product Example: CKM b sγ decay amplitude New Physics Wilson coefficient short-distance physics, perturbative at m W, RGE: m W m B can affect specific Wilson coefficients local operator effective Lagrangian Heavy Quark Expansion in power of Λ/m B can lead to introducing non-sm operators (e.g. right-handed currents) contribution of New Physics

5 b s Gluonic Penguins

6 Measurements of sin2β with s-penguin Modes Im (,0) Ru γ ( ρ,η) α UT Rt β 0 ( 1,0 ) Re

7 s-penguins: Compilation of Results time-dependent CP asymmetry mixing-induced direct pre-ichep06: Naïve average of s-penguin S coefficients 2.4σ away from reference value of sin2β (cc) ICHEP06 M.Hazumi plenary A.Lazzaro CPV K.Hara CPV New physics may affect different modes in different ways: use the pattern of deviations to go beyond the naïve average

8 Deviations from Standard Model Projected errors as a function of time 0.40 K*γ 0.35 f 0 K S 0.30 K S π φ K S 0.20 η K S 0.15 KKK S Error on sine amplitude Jan-03 Jul-03 Theory errors Jan-04 Jul-04 Jan-05 Jul-05 Jan-06 Jul-06 Jan-07 Jul-07 Jan-08 Jul-08 Jan-09 Jul-09 Significance of deviation from Standard Model expectation as a function of luminosity (assuming fluctuations around pre-ichep06 central values) Number of standard deviations BABAR+Belle in 2008 average η K S φ K S integrated luminosity (/fb)

9 Discriminating Among NP Models Exploit the pattern of deviations S in the various modes to discriminate among different models Wilson coefficients: Three NP models, six scenarios: NP only in the Z 0 -penguin coupling NP in Kaluza-Klein gluon excitations NP in chromo-magnetic operator Full analysis: for each model constraints in the plane of the two NP parameters (modulus and phase) Buchalla, Hiller, Nir, Raz (hep-ph/ ) S SM Six NP scenarios Exclusion vs luminosity

10 Flavor Mixing

11 Test Standard Model in B d Mixing Basic assumptions: no new Physics at tree-level 3-generation unitarity determine the apex of UT from V ub and γ Observables: Mixing amplitude contribution of NP SM SM favored (but NP not excluded) various analyses similar conclusions J.Charles (CkmFitter) hep-ph/ (2006) UTfit, hep-ph/ (2005) K. Agashe et al, hep-ph/ (2005) FJ.Botella et al, hep-ph/ (2005) Suggests mixing unaffected by NP one source of flavor & CP violation in Yukawa couplings (MFV)

12 b s Electroweak Penguins

13 Sensitive Probes of New Physics Examples of b s, EW-penguins: Radiative penguin (C 7 ) Z/photon penguin (C 7 & C 9 ) W-box (C 10 ) SM: top quark dominates in loops reliable calculations Many observables: rates (inclusive & exclusive) direct CP asymmetries, A CP (inclusive & exclusive) time-dependent CP asymmetries, S & C forward/backward asymmetries, A FB polarizations (photon, K* ) mass and angular distributions of lepton pair etc. with different sensitivity to New Physics

14 Radiative Decays: b s γ M.Convery HQ A.Limosani HQ The FCNC transition b s γ has been heavily studied by CLEO then by BABAR and Belle in a variety of ways exclusive (B K*γ) semi-inclusive fully inclusive Semi-inclusive analysis: sum of 38 exclusive modes (~44% of total) photon energy BABAR (88.9M BB) PRD72, (2005)

15 b s γ : Fully Inclusive Analysis efficiency corrected BELLE (152M BB) PRL93, (2004) Huge background subtraction systematic error dominated by off-resonance statistics BABAR (88.5M BB), hep-ex/

16 b s γ : Compilation of Results SM Predictions ~3.6 ± 0.4 x 10-4 NP B631, 219 (2002) NP B704, 56 (2005) EPJ C40, 165 (2005) So far all measurements are consistent with SM predictions (typical errors: <10%) A triumph for the Standard Model! Bounds on C 7 (sign not constrained) SUSY: probe LR mass insertions hep-ex/ Improvements (circa 2008) theory: NNLO 5% experiment: statistics x 4 and lower energy cut Direct CP asymmetry consistent with SM (~0)

17 B s l + l and B ) + K ( l l D.Kovalskyi CPV Exclusive branching fractions already measured with errors comparable to theory uncertainties CP asymmetries consistent with zero with large errors Ratio muon to electron mode sensitive to SUSY Higgs at large tanβ so far consistent with SM (=1) K* polarization consistent with SM SM C 7 C 7 Inclusive branching fractions C 7 C 7 SM q 2 /m 2 B inclusive BELLE, PR D72, (2005) BABAR, PRL 93, (2004) wrong-sign C 7 disfavored

18 B ) + K ( l l Forward-Backward Asymmetry Vector (C 7,C 9 ) and Axial-vector (C 10 ) interference Result K*ll: both experiments favor positive integrated asymmetry SM SM C 9 C 10 C 9 C 10 Crosscheck on Kll: A FB consistent with SM (zero) fit for leading term of effective Wilson coefficient SUSY: probe RR and LL mass insertions

19 Observation of b d γ Smaller SM amplitude higher NP sensitivity BELLE (386M BB) hep-ex/ evts D.Kovalskyi CPV BABAR (347M BB) CONF-06/ evts BABAR BELLE CDF 20.8 evts 5.9 evts 39 evts likelihood projections W.A.: no hint of New Physics yet 11 evts (NEW)

20 Right-Handed Currents in B K*γ? In the SM the photon is predominantly polarized (left-handed in b s γ) B 0 (K 0 S 0 π ) γ Therefore the final state is almost flavor specific and the TD asymmetry is suppressed N * K γ = 157 ± 16 (SM: ~ 0.1) If non-sm non-dipole contributions to the amplitude contribute larger values of S are possible large values of S probe non-standard polarization of the photon BABAR (232M) + Belle (275M) in K*(892) region ( GeV) So far no evidence for deviation from SM expectation (much higher statistics is required)

21 Leptonic Decays

22 B τν: Purely Leptonic Decay T.Browder CPV S.Sekula CPV W-annihilation hadronic tags Recoil technique (semileptonic and hadronic) semileptonic tags Select one & three prongs plot extra energy in calorimeter (GeV) BABAR (320M BB) CONF-06/028 combining 4 tau-decay modes BELLE (447M BB) CONF-0671 combining 5 tau-decay modes (3.5 standard deviations)

23 B τν: Constraints on 2HD-Models Charged Higgs contribution to the decay (no helicity suppression) In 2-Higgs doublet models coupled separately to up- and down quarks (incl. MSSM): (always destructive interference) Example of limits in tanβ-m(h ± ) plane using Belle s result and f B from unquenched lattice V ub from HFAG for b sγ : also charginos & squarks contribute various MSSM scenarios

24 More Leptonic Decays S.Sekula CPV hadronic tags no signal BABAR (230M BB) CONF-06/001 Limits at 90% C.L. no event 3 events BABAR (300M BB) CONF-06/026 SM: SM: No hint of New Physics in leptonic decays

25 FCNC in Charm Decays

26 D ) ( s h l l (h = π,k) & + + Λ c p l l Xc X u l + l SM: strong GIM suppression PR D66, (2002) BF ~ O(10-8 ) SM+SUSY SM BABAR (288/fb) hep-ex/ SM (short-distance) but Long-Distance contributions veto resonances (e.g. φ) BABAR (288 fb -1 ) place limits in the range (at 90%) goal: reach the 10-6 range and start to constrain SUSY

27 Conclusions Recent triumphs of the Standard Model Overall consistency of the CKM fit b s γ, b s l + l, b d γ, B τν, etc. Points of slight disagreement to keep an eye on tension between sin2β and V ub sin2β<0 (2.5-sigma) for s-penguin modes Kπ puzzle: ~2-sigma effect in B Kπ B factories to double their statistics in the next two years Standard Model in a very good shape New Physics in BB mixing? New Physics in b s-gluon? Complementarity of B-factory & flavor physics experiments with experiments at the energy frontier (Tevatron, LHC) Two main classes of New Physics models are favored by the data Minimal Flavor Violation (MFV) models with no new source of flavor & CP violation Beyond MFV new sources of CPV confined in b s transitions Results in flavor physics are crucial for NP model building

28 Physics Beyond the Standard Model at B Factories Gautier Hamel de Monchenault CEA-Saclay DAPNIA/SPP on behalf of the BABAR & Belle Collaborations ICHEP06, Moskow, 29 July 2006