Studies of rare B decays at LHCb Tomasz

Studies of rare B decays at LHCb Tomasz Skwarnicki Syracuse University

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki Bs, B 0 BR(Bs, d m+m-) w b t s, d 2 w nm m- SM m+ w b t s, d BRSM(Bs m+m-)=(3. 2 0. 2)x 10 -9 BRSM(B 0 m+m-)=(0. 10 0. 01)x 10 -9 Z 0, g w Vts , Vtd mm+ JHEP 1010, 009 (2010) • Very rare decays in SM: – PDG: the smallest measured BR in any B decay ~10 -6 – PDG: the tightest UL on any B decay BR < ~10 -7 • Small theoretical uncertainty • Excellent place to look for contributions from BSM: b Bs s H 0, A 0 m- NP m+ e. g. SUSY ~ tan 6 b Could be strongly enhanced. In some models negative interference with the SM. CDF 7 fb-1 7/12/11 PRL 107, 191801(2011) CDF 9. 6 fb-1 3/5/12 2. 1 s evidence for NP

Colliders and bb rates LHC design lumi CMS ATLAS 105 104 LHCb Upgrade LHCb Tevatron CDF, D 0 103 102 101 100 Let us catch NP in a loop lasso of truth Super(KEK)B hadron colliders 106 3 • Tremendous rate potential at hadron colliders 10 Ge. V e+e- colliders bb pairs produced (s-1) (within the angular acceptance) LHC Workshop, Chicago May 2012 Tomasz Skwarnicki • Collect all b-hadron species at the same time: – physics reach determined by the detector capabilities not by the machine – additional gain by a factor of ~10 -100 in integrated Bs rates at hadronic colliders • Charm rates factor of 10 higher than beauty rates: – nuisance and great physics opportunity at the same time

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 4 LHCb vs central detectors CMS LHCb • Some advantages of LHCb (forward spectrometer): – comparable bb cross-section in much smaller solid angle; smaller number of electronic channels; smaller event size; much larger trigger bandwidth to tape (~3. 5 k. Hz) – Dedicated heavy flavor experiment: b and c physics dominate the trigger bandwidth (e. g. CMS b-trigger rate in 2011 ~25 Hz; 2 orders of magnitude less than LHCb) – large p for small p. T (in central region p~p. T); can identify muons to lower p. T values • Limitation of LHCb: – luminosity limited by the detector readout capabilities

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki BR(Bs, d m+m-) 5 LHCb-PAPER-20120007 ar. Xiv: 1203. 4493 1 fb-1 (full 2011 statistics) • Analysis approach (log scale!) Boosted Decision Tree discriminator combining info from p. T, polarization angle, vertex displacement, isolation etc. Independent of the charged track ID. Uncorrelated with mmm. Flat for the signal Trained on signal and background MC but then signal and background distributions determined from the real data: B 0 h+h- for signal, mmm sidebands for the background m+ Exponential for the backgrounds m 1 fb-1 m+ Bs B 0 m. Estimate mmm resolution by interpolating from the observed resolution for J/y, y’, U, U’’ m+m- and B 0 h+h-

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 6 BR(Bs, d m+m-) normalization • Normalization of BR determined from 3 different control channels: Bd Bs BR / Nsignal (8. 4 0. 4)x 10 -11 (3. 2 0. 3)x 10 -10 According to SM BRs expect: ~10 Bs m+m~ 1 B 0 m+ mevents

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 7 BR(Bs, d m+m-) results 1 fb-1 Bs B 0 cut • Actual upper limits determined from the 2 D information without the BDT cut (97% of the sensitivity comes from the BDT>0. 5 data) BR(Bs m+m-) (1. 3 s below SM) BR(B 0 m+m-)

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 8 BR(Bs, d m+m-) implications From D. Straub @ Moriond E. W. (status after CDF 7 fb-1 results) (now LHCb 1 fb-1) Grey area excluded • SM has survived an order of magnitude improvement in the experimental sensitivity • Lots of room still left for NP before the experimental errors reach theoretical uncertainty in the SM predictions

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 9 BR(Bs, d m+m-) future • Bs, d m+m- are the easiest B decays to probe • CMS (ATLAS) have meaningful results (see Joel’s talk) and can become more sensitive in the next few years (until LHCb upgrade) thanks to larger integrated luminosities • LHCb upgrade needed to probe BR(Bs m+m-) with a sensitivity comparable to theoretical uncertainty on the SM predictions CMS 2011/12/17 5/20/100 fb-1 LHCb 2011/12/17 1 / 2 / 5 fb-1 LHCb upgrade 2018 - 50 fb-1

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 10 Search for D 0 m+m- LHCb-CONF-2012 -005 0. 9 fb-1 • Extremely small is SM: BRSM(D 0 m+m-)<6 x 10 -11 • Best limit from Belle PRD 81, 091102 (2010) <1. 4 x 10 -7 (90% CL) Normalization channel 1710 47 D*+ D 0 Feed-down Signal channel Fitted signal yield (1. 2 s from zero) LHCb preliminary <1. 1 x 10 -8

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 11 EW penguin: B 0 K*0 m+m. SM mm+ Z 0, g w B 0 b s d w + w t d mm+ K*0 B 0 b d nm t w s d K*0 • Look for interference of these SM diagrams. NP diagrams can contribute. • Need to eliminate effect of form-factors – various observables related to angular correlations. Most famous AFB F B

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 12 EW penguin: B 0 K*0 m+m. Before summer 2011: Ba. Bar: PRD 79, 031102 (2009) Belle: PRL 103, 171801 (2009) (4. 4 fb-1) New results: - CDF 164 - LHCb 900 (6. 8 fb-1) (1. 0 fb-1) 0. 4 0. 25 CDF 6. 8 fb-1 PRL 108, 081807 (2012) LHCB-CONF-2012 -008 1 fb-1 (theory=SM) (J/y, y(2 s) excluded) LHCB-CONF-2012 -008 1 fb-1

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 13 First measurement of AFB zero-crossing point

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 14 Asymmetry in transverse K 0* polarization We have also measured: BR(Bs fm+m-)=(0. 78 0. 01 0. 06 0. 28)x 10 -6 T-odd CP asymmetry Fraction of longitudinally polarized K 0* B 0 K*0 m+m- more observables • • • So far no challenge to SM Experimental errors statistics dominated and larger than theoretical uncertainty LHCb already has the most sensitive measurements: – 5 times more data by 2018 – 50 times more data with upgrade • LHCb upgrade will have better sensitivity than super e+e- factories in this exclusive channel (e+e- can also do inclusive measurement)

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki B+ p+m+m- 15 • b d transition, suppressed relatively to B+ K+m+m- by |Vtd|2/ |Vts |2~0. 05 BRSM(B+ p+m+m-)=(2. 0 0. 2)x 10 -8 • Could be larger in non-SM Belle PRD 78, 011101 (2008) LHCb < 7. 0 x 10 -8 (2. 4 0. 6 0. 2)x 10 -8 LHCb-CONF-2012 -006 events 5. 2 s Rarest B decay ever detected!

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 16 Other new rare decay results • Search for B 0 m+m- (first limits) LHCb-CONF-2012 -010 • Search for majorana neutrino in B- X+m-m(tightest limits) LHCb-PAPER-2011 -038 ar. Xiv: 1201. 5600 • Measurement of direct CP asymmetry in B 0 K*0 g (consistent with zero, best measurement) LHCb-CONF-2012 -004 • Most precise measurement of direct CP asymmetry in B 0 K+p- (6 s away from zero), first observation of CP violation in Bs K+p- (3. 3 s away from zero) LHCb-PAPER-2011 -029 • Time dependent measurement of CPV in Bd, s hh (direct CP asymmetry term in B 0 p+p- favors Ba. Bar results) LHCb-CONF-2012 -007

LHC Workshop, Chicago May 2012 Tomasz Skwarnicki 17 Conclusions • LHC is a beauty and charm factory foreseeable future: – Unique reach in Bs physics. Best sensitivity in many Bd, u, D measurements. • LHCb is the first hadron collider experiment dedicated to heavy flavor physics – The recent results have proven that a broad beauty and charm physics program at a hadronic collider is possible with quality of results matching the e+e- factories. – Reaching new levels of sensitivity (i. e. higher energy scales) in many key measurements: • No indication of NP in beauty decays yet. Plenty of room for NP before theoretical limitations are reached. • NP seen in D 0 decays [ACP(K+K-)-ACP(p+p-)] ? • More data to be collected in next few years – Channels with many neutrals and neutrino(s) will remain exclusive domain of the e+e- factories. • Physics reach limited by the detector capabilities not the collider: – LHCb upgrade in 2018.