clfv & BNV LHCb Gerco Onderwater on behalf of the LHCb collaboration

Transcription

1 clfv & BNV LHCb Gerco Onderwater on behalf of the LHCb collaboration Flavour2017, Qui Nhơn, Việt Nam, August 2017

2 2 34 Outline LHCb Experiment LFV with muons : τ LFV with electrons : D0 e LFV with taus? BNV & LNV Conclusion B+ τ ντ K+

3 3 34 LHCb

4 4 34 LHCb : precision measurement RICH Trigger PID ε(k) ~ 95% for MisID( K) ~ 5% high efficiency esp. muon triggers VELO IP resolution 15+29/(pT/GeV) m Tracking Δp/p 5 GeV/c 200 GeV/c Muon ID identification ε ~ 97% misid ~ 2% Int. J. Mod. Phys. A 30, (2015)

5 5 34 Recent LHCb results D0 e PLB 754 (2016) 167 LFV B0 D*+ τντ / ν PRL 115, (2015) LNU τ JHEP 02 (2015) 121 LFV B+ K+ / ee PRL 113, (2014) LNU B + PRL 112, (2014) LNV τ p PLB 724 (2013) 36 BLNV + D(s) ++ PLB 724 (2013) 203 LNV B0 e PRL 111 (2013) LFV Julian Julian

6 6 34 τ detection

7 7 34 Challenge : τ decays at hadron collider LHC B factory Babar & Belle ~3x109 τ-pairs LHCb ~3.5x1011 τ's in detector acceptance in 2011 & 2012 e+e τ+τ extremely clean Nearly no direct τ production, mainly from Ds decay tag with opposite τ possible No production traces in Ds τντ Charm decay with missing particles similar to τ signature

8 8 34 τ 3 search main tau production via decay of Ds Approach: trigger on muon and secondary vertex multivariate analysis to discriminate signal and background control sample for normalization and calibration ν τ primary vertex Ds secondary vertex JHEP 02 (2015) 121

9 9 34 Signal candidate selection Trigger muons not in beampipe (pt > 1.48 GeV/c) two-, three- or four-track secondary vertex at least one particle does not point to collision point Analysis no tracks may point to collision point good 3-track vertex decay-time compatible with τ decay (ct > 100 m) τ momentum must point back to PV misid Background elimination M(+ ) M(Φ) > 20 MeV/c² M(+ ) > 450 MeV/c² M( ) > 250 MeV/c² Ds Φ(+ ) missing mis-reconstructed Ds η(+ γ) ν reconstructed from same particle JHEP 02 (2015) 121

10 10 34 Signal & background discrimination Three likelihoods to distinguish signal from background I. L3body : decay topology L3body II. LPID : identification III. L3 : tau selection LPID

11 11 34 M3 distribution Shape determined using Ds Φ(+ ) Analyze 5x5 best bins in LPID and L3body Blind analysis LPID L3body : [0.65, 1.0] : [0.725, 1.0] JHEP 02 (2015) 121

12 12 34 M3 distribution Shape determined using Ds Φ(+ ) Analyze 5x5 best bins in LPID and L3body Bkgd Signal Bkgd LPID L3body : [0.65, 1.0] : [0.725, 1.0] JHEP 02 (2015) 121

13 13 34 Result Robust analysis method Statistics limited No significant evidence for excess of events dashed : expected solid : observed B(τ + ) < 4.6 x % C.L. 95% 2.1 x 90% C.L. 68% BaBar 3.3 x 90% LHCb may overtake Belle which will then be overtaken by Belle-II JHEP 02 (2015) 121

14 14 34 e D0 e detection

15 15 34 D0 e Belle : Br(D0 e) < 2.6x10 7 (90% CL) RPV SUSY : ~10 7 Leptoquarks : 4x10 8 LHCb analysis based on 3 fb 1 s = 7 & 8 TeV D*+ D0 + D0 e Signal D0 K + Normalization + D0 e D*+ PLB 754 (2016) 167

16 16 34 Bremsstrahlung e eγ also study w/ B+ J/ψ K+ e+e PLB 754 (2016) 167

17 17 34 Mis-Identification + Probability for + e mis-id ~ (1 2)x10 8 K PLB 754 (2016) 167

18 18 34 Unbinned simultaneous fits Signal + bkgd BKGD-like D0 e (signal) -7±15 events intermediate Signal-like m(e) MD m(e)-m(e) MD*-MD PLB 754 (2016) 167

19 19 34 Result Robust analysis method Statistics limited No significant evidence for excess of events dashed : expected solid : observed B(D0 e) < 1.3 x 90% C.L. 20x improvement over previous result Effectively deal with backgrounds Bremsstrahlung complicates analysis PLB 754 (2016) 167

20 20 34 Other channels under investigation B(s) e B0 Bs K*0e Φe B(s) J/Ψ( e) X B+ K+e Expect to improve existing limits

21 21 34 τ r o f s e i t i n u t r o p p O detection

22 22 34 Some existing limits J/ψ(1S) τ < 2x10 6 Υ(1S) τ < 6x10 6 Υ(2S) τ < 3x10 6 Υ(3S) τ < 3x10 6 Z0 τ < 1x10 5 h0 τ < 1.5% J/ψ(1S) eτ < 9x10 6 Z0 eτ < 1x10 6 O(few x 90-95% CL Particle Data Group

23 23 34 Reconstruction I Interesting possibility Short lifetime prohibits direct detection B0 τ

24 24 34 Reconstruction II Interesting possibility Short lifetime prohibits direct detection Neutrinos remain undetected B0 τ ντ ν

25 25 34 Reconstruction III Interesting possibility Short lifetime prohibits direct detection Neutrino remains undetected Br ~ 9% B0 τ ντ

26 26 34 Reconstruction IV Interesting possibility Short lifetime prohibits direct detection Neutrino remains undetected B+ τ ντ K+

27 27 34 Reconstruction V Interesting possibility Short lifetime prohibits direct detection Neutrino remains undetected τ ντ

28 28 34 Possibly interesting channels B0 B(s) e/τ τ ντ B+ B+ ντ τ K+e/τ K+ Υ(nS) e/τ τ ντ Benefit from B0 D*+τντ & B(s) ττ Phys. Rev. Lett. 115, (2015) Phys. Rev. Lett. 118, (2017)

29 29 34 BNV & LNV

30 30 34 LHCb LNV & BNV results B D*+ D0+ D+ Ds+ < < < < 2.4x x x x10 7 K+ + < 5.4x10 8 < 4.0x10 9 Ds + < 1.4x10 7 D + < 2.5x10 8 τ p p++ < 5.4x10 7 * < 4.6x10 7 Search for Majorana ν's Best limits to date, still to be improved Note: B L not conserved (except *) PRL 112 (2014), PLB 724 (2013), 36 PLB 724 (2013), 203 PRL 108 (2012), PRD 85 (2012),

31 31 34 LNV / BNV / (B L) conserving p p B0(s) Λc Λ0(b) K+ Λ0b D+(s) Λ+c ++ M0 B+ ℓ B0 M+ ℓ B+ ℓ+ℓ+ℓ Being investigated D0 B0(s) (0,0) (+1,+1) ( 1,0) (0,+1) (+1,0) (0, 1)

32 32 34 Conclusion

33 33 34 Take away message LHCb : diverse program studying flavor physics with all three quark & lepton generations With LHC Run-I data LHCb sharpened limits for many LFV, LNV, and BNV channels No significant deviations from SM seen Demonstrated sensitive BSM hadron collider Many more options around, lots of additional data expected in Run-II & Run-III

34 Thank you for your attention!