Perspectives in B Physics: Results from LHCb

Transcription

1 Pheno 2017 Symposium Pittsburgh, May 8 th, 2017 Perspectives in B Physics: Results from LHCb Ulrich Uwer Heidelberg University on behalf of the LHCb Collaboration Outline: b s Introduction Unitarity Triangle Meson Mixing Rare B decays Supported by 1

2 Quark sector in Standard Model Yukawa couplings to Higgs Quark masses 6 parameters V CKM Flavor transitions across generations = V V V ud cd td V V V us cs ts V V V ub cb tb 3 +1 parameters Rich phenomenology, well tested but very puzzling! 40 years: Discovery of the ϒ [S. W. Herb et al. Phys. Rev. Lett. 39, 245 (1977)] 2

3 3 Effect of quark mixing - FCNCs B 0 B ps ± = d m Phys. Lett. B 719 (2013) B 0 B d t t b b d W W d u s c b t

4 Effects of CKM Phases CP Violation Example of CP violation: B ± π ± KK LHCb, PRD 90 (2014) B + π + KK B - π - KK Remark: So far CPV has been seen only in meson decays. Recently LHCb reported evidence for CPV in baryon decays: CPV in Λ b pπ - π + π - w/ 3.3σ Nature Physics (2017). arxiv:

5 New Physics in Quantum-Loops Standard Model New Physics W t + Y X A SM + A NP A BSM A 2 c rates SM c = A mw Λ NP Phase CP-violation Lorentz-structure angular distr. Search for deviations from Standard Model predictions: Suppressed processes, observables w/ small theoretical errors High-rate experiments to maximize sensitivity: LHC(b) / Belle-2 5

6 Heavy flavor production at LHC(b) σ ( pp bbx ) 7 TeV: 295 µb 13 TeV: 600 µb σ ( pp ccx ) 20 σ PRL 118, (2017) bb p b x1 x2 p b Run 1 (in LHCb acceptance) pp: cc: ~ 3fb -1 bb: Limit visible bunch cross. to ~1.1 L cm -2 s -1 (levelled) Run I Run II Run 2: 2 fb -1 at 13 TeV effect. data: 2 6

7 Heavy flavor production at LHC(b) σ ( pp bbx ) 7 TeV: 295 µb 13 TeV: 600 µb σ ( pp ccx ) 20 σ PRL 118, (2017) bb p b x1 x2 p b Run 1 (in LHCb acceptance) pp: cc: ~ 3fb -1 bb: Limit visible bunch cross. to ~1.1 L cm -2 s -1 (levelled) Run I Run II Run 2: 2 fb -1 at 13 TeV effect. data: 2 7

8 Searching for NP - selected LHCb measurements CKM Metrology B s - Mixing A mix = A i mix e φ mix Rare decays - FCNCs µ µ 0 B 0 K angular distribution γ via direct CPV sin2β via t-dep. CPV V ub semilept. decays Mixing and mixing phases B d,s rates + µ µ D 0 Mesons Mixing and CP violation Penta-Quarks: PRL 115 (2015) Quark exotics arxiv: ; arxiv: Ω c states arxiv: Hadron Spectroscopy 8

9 Unitarity Triangle CKM Metrology LEP, KTeV, NA48, BABAR, Belle, CDF, DØ, LHCb, CMS, ATLAS, ckmfitter.in2p3.fr 9

10 Unitarity Triangle CKM Metrology LEP, KTeV, NA48, BABAR, Belle, CDF, DØ, LHCb, CMS, ATLAS, 2016 ckmfitter.in2p3.fr Over-constrain triangle: trees loops (γ, V ub sin2β m s & m s ) 10

11 CKM-Phase γ Interference between b c and b u DK r B leads to direct CP violation in B DK decays Interference requires the D 0 (D 0 ) to decay into a common final state: f D = KK, ππ (CP state) f D = Kπ and πk (CKM favored/suppressed) f D = self conjugated Dalitz-modes Gronau, London, Wyler (GLW) Atwood, Dunietz, Soni (ADS) Giri, Grossman, Soffer, Zupan (GGSZ) Theoretically clean. However, single measurement not very sensitive (BR ~10-7 ). Need to combine many decay modes. 11

12 Two examples for B DK ADS GGSZ B ± (Kπ) D K ± mode (BR ~ 10-7 ) was soon seen at LHCb. Being exploited for high-precision CP-violation measurements. B - [π-k + ] D K - B + [π+k - ] D K + CPV B - / B + differences in multibody phase space (D K S ππ or K S KK) Benefit from the high purity of signal. CPV JHEP 10 (2014) 097 PLB 760 (2016)

13 Combination of γ (B DK) JHEP 12 (2016) 087 time dependent γ = ( ) o Agrees with BaBar and Belle and with prediction from CKM fits BaBar Belle Indirect γ = γ = γ = (69 (68 (65.3 ) + 17 o o 14) ) o PRD 87, (2013) arxiv: (2013) CKM Fitter 2006 Aim for 3-4 o uncertainty after Run-2. The LHCb-Upgrade will allow for even higher sensitivity (~1 o ). 13

14 CKM Phase β PRL 115, (2015) V td e φ 0 B i M A = M mix A mix Interference mixing and decay φ f CP β V arg V cd cb * td V V * tb SM: φ M = 2β 0 B time dependent CPV: A ( t ) ~ η sin 2β sin( mt ) Golden decay B 0 J/ψK s (42560 evts) sin 2β = 0.731± ± (Stat. error BaBar: ±0.036 Belle: ±0.029) CP CP World average (HFAG) 0.69±0.02 Tensions w/ indirect value from CKM-Fit:

15 Unitarity Triangle : V ub V ub measurement thought impossible at LHC ~ V ub Nature Physics 10 (2015) 1038 Use baryon decay Λ b pμν, benefit from RICH & vertexing capabilities. Normalize to Λ b Λ c μν and use lattice QCD to interpret result. V ub = (3.27 ± 0.15 ± 0.16 ± 0.06) 10 errors: exp LQCD from V cb 3 Λ b pμν Constraint on LH & RH coupling Different LQCD calculations 15

16 B s - Mixing New J. Phys. 15 (2013) LHCb B s B s B s B s 0 B s A mix? = 0 B s m s = ± ± ps -1 Theorie (U.Nierste, 2012) m s = 17.3± 1.5 ps -1 = Amix i e φ M ( ts ) s φ 2 M φs 2 argv β time-dependent CP asymmetry to measure φ s 16

17 Golden mode : B s J/ψφ(KK) m(kk) 1.02 GeV (φ region) φ s = ± ± 0.006rad Γ= ± ± ps -1 PRL 114, (2015) 53k evts m(kk) > 1.05 GeV (above φ) φ s = 0.12 ± 0.11±0.03 rad Γ=0.066± 0.018±0.019 ps -1 arxiv: arxiv: k evts New LHCb average for φ s φ s = 0.7 ± 37.3 mrad (includes also B s J/ψππ, D s D s data) 17

18 Weak phase φ s ATLAS and CMS have also measured φ s in B s J/ψφ with full Run-1 statistics. Impressive progress since initial measurements by CDF and D0: Uncertainty needs to be further reduced to reach SM precision. LHCb sensitivity after upgrade expected to be better than 3 mrad. 18

19 CP Violation in B-mixing 19 µ X µ + X B 0 B 0 B 0 B 0 CP s d q X B B X B B X B B X B B a q q q q q q q q q sl,, ) ( ) ( ) ( ) ( = + Γ Γ Γ Γ + + µ µ µ µ PRL 117, (2016)

20 CP Violation in Charm LHCb-CONF Direct CP violation: A CP (D 0 h + h -) - time integrated - D*-tag: A CP = ( ± 0.08 ± 0.03) % PRL 116, (2016) µ-tag: A CP = (+0.14 ± 0.16 ± 0.08) % JHEP 07 (2014) 041 PL B767 (2017) Measurement of A CP (KK) LHCb combination A CP (KK) = (0.04 ± 0.12 ± 0.10) % A CP (ππ) = (0.07 ± 0.14 ± 0.11) % PL B767 (2017) 177. Most precise measurements from a single experiment. No evidence of CP asymmetry. 20

21 CP violation time dependent arxiv: A Γ (KK) = (-0.30 ± 0.32 ± 0.10) 10-3 A Γ (ππ) = ( 0.46 ± 0.58 ± 0.12) 10-3 LHCb Run-1 combination A Γ = ( ± 0.28) 10-3 HFAG arxiv: arxiv:

22 Rare (FCNC) B Decays µ µ 0 B 0 K B d,s + µ µ 22

23 Very rare decays B d,s 0 µ + µ - Standard Modell: SM prediction: PRL 112 (2014) BR(B s μ + μ - )= (3.65 ± 0.23)x10-9 BR(B d μ + μ - )= (1.06 ± 0.09)x10-10 Sensitive for New Physics: (pseudo) scalar interactions D.Straub, arxiv:

24 Combined CMS & LHCb Analysis Nature, 522, (2015) arxiv: CMS & LHCb also: Interesting sociological experiment B 0 d >3σ B0 s >6σ 24

25 LHCb B s,d μμ update Include 1.4 fb -1 from Run-2: effectively doubles the dataset. Refined analysis: better background rejection arxiv: σ observation of B s µµ: +0.3 BR(B s µµ) = (3.0 ± 0.6 ) No evidence yet for B d µµ: BR(B d µµ) < (95%CL ) arxiv: Measurement from ATLAS 25

26 Measurement of effective lifetime Effective lifetime sensitive to scalar vs non-scalar New Physics contributions. PRL (2012) arxiv: A Γ depends on effective lifetime τ µµ 26

27 b s penguins: B K*l + l - and friends Standard Model: O7 O 9 O10 Different q 2 probes different processes New Physics: New operators (Lorentz structure / µµ/ee coupl), modified Wilson coeff. Observables: differential BR, angular distributions or lepton flavor violation 27

28 B K*l + l - and friends: differential BR Consistent tendency to undershoot prediction at low q 2. Intriguing! 28

29 B K*l + l - and friends: angular analysis Wu-Experiment with B-mesons JHEP 02 (2016) 104 Forward-backward asymmetry A FB = N N F F N + N B B SM: Altmannshofer, Straub EPJ C75 (2015) 382. K* longitudinal polarization General pattern as predicted, mild tension (e.g. A FB ) at low q 2 other observables, which can be built from the measured amplitudes 29

30 B K*l + l - and friends: angular analysis Constructed to be intrinsically robust against form factor uncertainties, JHEP 02 (2016) σ (4-8 GeV 2 ) (physically hard to visualize) Effect seen with 1 fb -1, persists with 3 fb -1 SM: Descotes-Genon et al., JHEP 12 (2014) 125, Results encouraged the B-factories to dig deep into their data Belle, arxiv: and als ATLAS and CMS presented measurements at Moriond 2017 (Run 1) ATLAS-CONF CMS-PAS-BPH

31 B K*l + l - and friends: lepton universality Observed tensions w/ µµ final state. Do electrons behave the same way? Electrons are a bit more difficult PRL 113 (2014) Very clean observable: Test of lepton universality in R K ± ± B ( B K µµ ) R K = ± ± B( B K ee ) SM = (measured as double ratio, relative to B KJ/ψ(ll) ) 1 B KJ/ψ(e+e - ) control region LHCb measurement for 1<q 2 <6 GeV 2 B Ke+e - Low q 2 region -2.6σ w/r to SM PRL 113 (2014) Statistical fluctuation? What about R K *? 31

32 Measurement of R K* ( in preparation) LHCb-PAPER Analogous measurement for B K*l + l - R K * 0 0 B ( B K µµ ) = B( 0 0 B K ee ) Again measured as double ratio normalized to B 0 K*J/ψ(µµ,ee) 3 exclusive triggers for K*ee: On electron, On K*, Not On signal Simulation corrected w/ efficiencies (PID, trigger) determined on data, Cross-check: B(B 0 K* J/ψ) is measured for muon and electron channel a stringent test! 90 evts 110 evts Analysis performed in two q 2 bins Low: 4m µ2 < q 2 < 1.1 GeV 2 Central: 1.1 GeV 2 q 2 < 6 GeV 2 Muon sample 3-5x larger 32

33 R K* Results ( in preparation) LHCb-PAPER σ σ Systematics: correction of simulation Kinematic selection Residual background due to B 0 K* J/ψ % for central q 2 (depending on trigger sample) 33

34 B K*l + l - and friends: Interpretation? Before the measurements of R K* : Fits give >5σ pulls w.r.t. SM allowing for non-sm Wilson coefficients (C 9 ) improves the p-value of the fits. [arxiv: ] New R K* measurement: Fits into this picture (certainly for the central q 2 bintriggered a several papers. Example: arxiv: Situation intriguing - more work needed: Theory: Theoretical error of some observables. Experiment: LHCb Run-2 updates on R K, R K* and even R φ 34

35 Other Hints for LFV PRL 115 (2015) R(D*) B(B D*τν) / B(B D*µν) B D*τν : Tree decay, not rare, only difficult sensitivity to possible charged Higgs B-factory legacy BaBar & Belle Was thought to be impossible at LHCb (cannot reconstructing full event): LHCb Reconstruct τ µνν disentangle signal from B 0 D*μν and other backgrounds by fitting E µ * and m* miss2 (rest frame of B) in bins of q 2 35

36 R(D*) B(B D*τν) / B(B D*µν) +2.1σ above SM PRL 115 (2015) Systematics dominated by model uncertainties. Belle 2016 LHCb New HFAG average 3.9σ away from SM prediction (0.252±0.003). New measurements including R(D*) w/ τ πππν will come soon 36

37 At the End Precision flavor physics is an excellent tool to search for effects of New Physics beyond the TeV scale. Flavour-physics measurements at the LHC are adding to the impressive knowledge from the B-factories and Tevatron. Many of these results show good compatibility with the SM (for now), some signs of tension (LFV) are emerging. LHCb s physics program beyond flavour physics: EW precision measurements, direct NP searches, forward physics, fixed target physics, heavy ion physics Future: 8 fb fb -1 Supported by Interest HL LHCb 50 ab fb -1 37

38 Backup 38

39 Spectroscopy: New Ω c states arxiv:

40 Spectroscopy: New Ω c states arxiv:

41 J/Ψp resonances - pentaquark states PRL 115 (2015)

42 Four-quark exotics: J/ψΦ-structures arxiv: arxiv: Long standing interest in J/ψΦ spectrum in B + J/ψΦK +, where CDF saw a narrow structure [PRL 102 (2009) ] dubbed the X(4140). Confirmed by D0 [PRD 89 (2014) ] & CMS [PRL B 734 (2014) 261], but not by LHCb in early 0.37 fb-1analysis [PRD 85 (2012) (R)]. A good description of spectrum requires four (!) non-standard contributions, all of which are present at >5σlevel. X(4140) found to have larger width than previous analyses, and its quantum numbers are found to be This structure can also be described by a below threshold DsDs*cusp. 42

43 SEARCH FOR X(5568)± PRL 117 (2016)

44 Combination of γ (B DK) JHEP 12 (2016)

45 Possible Interpretation Attempts to explain the V ub inclusive vs exclusive puzzle with help of righthanded currents: different sensitivity of the baryon result disfavors hypothesis LHCb result provides new ways to access V ub. Look for complementary measurements, e.g. with Bs Kμν. 45

46 Constraints on New Physics SM + NP arxiv: A mix = A = A SM mix SM mix + A NP mix ( 1+ ) B 0 s B 0 d ( bs) ( bd) < 20% < 30% NP Need to increase precision to disentangle NP phases of few degrees in Bd and Bs mixing 46

47 Systematics of R K* 47

48 Physics Reach Obervable LHCb 2017 (7 fb -1 ) B s Upgrade (+ 50 fb -1 ) Theory Uncertainty Mixing ~0.003 phase φ s BR(B s µµ) BR(B d µµ) / BR B s µµ ~100% ~35% ~5% CKM angle γ 4 o 0.9 o small CPV in D ( A CP )