1 Part III: some first physics from LHCb

2 LHCb physics menu b s from trees: B s -> J/psi phi,... CP asymmetries rare decays b s from penguins: B s --> jj, B s --> jg,... g from trees: B - -> D 0 (CP) K - g from penguins: B d,s --> h + h - g from mixing: B s --> D s K Bs --> mm, Bd -- > mm Bd --> K* mm, Bd -- > Kmm Bd --> K* g, Bs -- > jg for details, see the LHCb roadmap document in this talk: some recent highlights

3 integrated luminosity in 2010 ● LHCb recorded about 38/pb in 2010 ● about 2x10 12 inelastic crossings, about b-bbar in acceptance ● 1, billion events, 64 TB of raw data ● integrated lumi very close to ATLAS/CMS ● this will change in why? LHC in 2010 ÖS = 2 x 3.5 TeV max L inst = ~10 32 / cm 2 s

4 ● LHCb optimized to run with less than 1 interaction/BX ● in 2010 reached 'design lumi' (!) but with fraction of bunches design ● higher mu means ● fuller events, degraded reconstruction performance ● more background, worse flavour tagging (?)

5 s(pp ® bb X) at 7 TeV ● movitation ● comparison to QCD predictions ● important input for estimating LHCb potential ● method ● select b --> D0 m n X decays (inclusively) ● use known branching fraction b b p proton p known fraction ends up in B meson known fraction ends up in D 0 mnX b q q c W-W- m-m- n u D0D0 X

6 s(pp ® bb X) at 7 TeV ● D 0 selected in K + p - final state ● most D 0 are 'prompt' ● select D 0 from b with impact parameter K p from b decay: prompt: K p D0D0 D0D0 B prompt from b

7 s(pp ® bb X) at 7 TeV ● purity strongly enhanced by combining D 0 with muon ● background estimated with 'wrong-sign' combinations D 0 m - combinations D 0 m + combinations

8 s(pp ® bb X) at 7 TeV ● cross-section versus pseudo-rapidity ● after extrapolating to full phase space largest systematics ● ● fragmentation fractions ● extrapolation to full phase space (and all of of this using just the first 14 nb -1 ) good agreement with predictions

9 Near future: CPV from semi-leptonic decays ● D0 experiment: take events with two b --> X l nu, then look at 'like- sign' muon combinations b W-W- m-m- n b W+W+ m+m+ n unlike-sign: unmixed b W-W- m-m- n b W-W- m-m- n X b like-sign: mixed ● an asymmetry between positive like-sign and negative like-sign yield is caused by CP-violation in mixing SM ● this asymmetry is expected to be very small in the SM

10 Near future: CPV from semi-leptonic decays ● D0 measures the sum of Asl in Bd and Bs decays ● about 3 sigma away from SM SM ● however, complicated measurement ● m + vs m - reconstruction efficiency ● asymmetry in background (e.g. decays in flight, K+ vs K-) ● what can LHCb do?

11 Near future: CPV from semi-leptonic decays ● competing with D0 measurement is hard ● production asymmetries (pp vs pp) ● cannot flip field as often as D0 ● instead, look at b --> D X mn ● advantage: can separate B s and B d ● now measure difference in Asl(Bs) and Asl(Bd) ● complementary to D0 measurement

12 B-> h + h - ● two body B decays (B d,s -> K + p -, p + p -, K + K - ): ● important control channel for B d,s --> m + m - ● extraction of angle g

13 CP violation in B s,d --> K + p - ● necessary ingredient: two amplitudes with different phases exercise: what are the relevant diagrams for B s --> Kp? ● expect 'direct' CP violation (charge asymmetry) in SM d is a poorly known strong phase

14 CP violation in B s,d --> K + p - BdBsBdBs ● large CP violation in both B d and B s to Kp ● it took B-factories years to establish this! ● need another factor 10 in statistics to overtake CDF and B-factories ● note that mass resolution is really important here

15 CP violation in J/yj ● as Niels explained ● CP violation in J/yj provides very clean measurement of b s ● almost zero in SM: sin(2 b s )= 0.04, compared to sin(2 b)= 0.7 ● sensitive to NP scenarios affecting b --> s transition ● first measurement by Tevatron experiments note: f s = -2 b s

16 J/yj in first LHCb data ● about 1100 candidates in first 33/pb ● 100x less than yield in 'nominal' LHCb year ● 6x less than CDF and D0 ● what does it take to measure bs? B candidate mass propertime B signal combinatorial 'prompt' background

17 measuring oscillations Bs->Ds–  (2 fb-1) Experimental Situation: Ideal measurement (no dilutions)

18 measuring oscillations Bs->Ds–  (2 fb-1) Experimental Situation: Ideal measurement (no dilutions) realistic flavour tag dilution

19 measuring oscillations Bs->Ds–  (2 fb-1) Experimental Situation: Ideal measurement (no dilutions) realistic flavour tag dilution realistic proper time resolution

20 measuring oscillations Bs->Ds–  (2 fb-1) Experimental Situation: Ideal measurement (no dilutions) realistic flavour tag dilution realistic proper time resolution background proper time acceptance understanding the dilutions from flavour tagging and resolution is essential for any measurement involving mixing

21 tagger calibration ● input to the flavour tag ● same-side tagger: charge of Kaon close in phase space ● opposite-side tagger: charge of lepton of Kaon from other B ● taggers are calibrated with “flavour-specific” final states ● a final state that tells you what the flavour is at time of decay ● can used both neutral (mixing) and charged (non-mixing) B decays ● example, take B+ --> J/y K+ ● the charge of the Kaon tells you if this was b or b-bar ● the tagging algorithm computes tag based on full event ● now count the fraction of times that the tagger was wrong miss-tag-rate: probability that tag is wrong

22 tagger calibration ● oscillation signal from B0 --> D* - mn so, we see oscillations (25 years after Argus :-) ● expect oscillation to have 'unit' amplitude ● amplitude of the oscillations gives estimate of dilution

23 resolution calibration ● proper time resolution can be estimated from negative side of proper time distribution J/psi phi candidates prompt events on negative side are all due to resolution effects prompt background

24 extra-complication: decay angles ● Niels maybe told you: J/psiPhi is actually superposition of two CP eigenstates ● need to be separated with 'complicated' angular analysis ● see for example Tristan Du Pree's thesis ● final angle bs extracted from a likelihood fit with about 8 physical obervables and tens of calibration parameters transversity (or helicity) angles describe decay topology: angles of muons and Kaons in B frame

25 'cross-check' measurements sin(2b) in B 0 -> J/y Ks angular amplitudes in B 0 ->J/y K* B s mixing in B s --> D s p to convince the world that we know what we are doing, we will need to measure some things that are already well known

26 b s expectation ● sensitivity to 2bs (provided 'tagging' works as in simulation) ● current expectation for Moriond: uncertainty about as large as CDF and D0 ● will need to do a lot of work though... make sure to ask Daan every day about it!

27 B s --> m + m - ● very rare decay in SM: BR = ( ) x ● mainly Z-penguin and W-box ● helicity suppressed, CKM suppressed ● theoretical uncertainty small ● large possible beyond-SM contributions ● e.g. in MSSM: BR ~ tan(b) 6

28 B s --> m + m - analysis strategy ● select dimuon pairs ● then take those that fly 'far' measure of how much it 'topologically' looks like a B

29 B s --> m + m - expectation ● with 2010 statistics, LHCb is about competative with CDF an D0 ● wait for Moriond! ● with about 1/fb LHCb (end 2011?) LHCb can discover NP if it enhances the branching fraction by a factor 5

30 summary ● LHCb is a forward spectrometer dedicated to beauty and charm physics at the LHC ● detector up and running, first serious results coming out ● best bet for NP: b --> s transitions ● CP violation in Bs --> J/yj ● very rare decays: Bs --> m+m- ● other very important topics ● angle g, the least well known angle ● forward backward asymmetry in B --> K*m+m- ● CP violation in radiative decays: B  K*g, B  fg ● charm physics: D 0 mixing, CP violation ● non-standard Higgs decays, exotic new particles,... ● don't be surprised if this is where NP will turn up first!