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BsDsh and BDh Decays in LHCb

Steven BluskSyracuse University

On behalf of the LHCb Collaboration

Beauty 2011, Amsterdam, The Netherlands, April 4-8, 2011

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Introduction

B decays provide an excellent laboratory to search for NP in box/loop diagrams Tremendous progress in the last decay

(BaBar, Belle, CLEO, CDF, D0, Lattice…) New Physics not dominant

But, there is tension/hints. 2-3s deviations in sin(2b) Large direct CPV in BKp. Maybe hints in sin(2bs), although clearly we

need to shrink errors here. D0 Asl tantalizing, needs confirmation

While errors have been slowly shrinking, we are in great need of precise, “NP-free” measurements. Direct g dominated by trees ~NP free Will play a crucial role in sorting out NP

scenarios in the CKM paradigm.

If NP exists, (and its couplings to the quark sector are not highly suppressed), there should be observable/sizeable effects in loop-mediated diagrams.

E. Lunghi and A. Soni arXiv.1010.6069v2

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Angle g in LHCb• Time-independent (ADS, GLW, GGSZ, etc)

– E.g. B- D0K- B0 D0K*0 B- D0K-p+p-

• Time-dependent – E.g. BsDs

+K-, BsDs±K-p+p-

B0D-p+ B0D-p+p-p+

• Challenges:– Sensitivity through bu low rates– Excellent PID critical, e.g. DCS D0Kp– Fully hadronic mode, triggering,

backgrounds

• Key strengths of LHCb (for g)– Large b production rate: ~100 kHz bb– Excellent PID: 2 RICHs, eK~95% , O(<5%) p-K misid– Excellent proper time resolution (needed for time-dependent

analysis)– Trigger: next slide

A few words on triggering• Sensitivity to g through hadronic final states hadronic trigger crucial.

• L0: require 2x2 calorimeter cluster with ET>3.6 GeV. eL0/eoff-sel ~ 45%

• HLT:– HLT1: Require a single track with pT>1.25 GeV, p>12.5 GeV and IP>125 mm.

• eHlt1/eoff-selxL0 ~ 80-90%– HLT2: Form 2, 3, and 4-body states, among tracks with IP c2>16,

pT>0.5 GeV, p>5 GeV. • eHlt2/eoff-selxHlt1xL0 ~ 80-90%

• Signal on tape is comprised of events where we:– Trigger On the Signal (TOS)– Trigger Independently of the Signal (TIS) : generally from the other b

– L0: ~50% TOS & ~50% TIS – HLT1 & HLT2: ~90-95% TOS, O(10%) TIS

– Some analyses use TOS only, some TOS & TIS

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LHCb in 2010•In 2010, LHCb collected ~37 pb-1 of data– Only 2.5% of a nominal LHCb year, but:

• Enough to demonstrate capabilities in key channels• Already able to make world class measurements, including several first observations.

•Today, I will present:– Measurement of B0DK- [LHCb-CONF-2011-013]– First observation of BsD0K*0 [LHCb-CONF-2011-008]

– New measurements of XbXcppp and First observation of BDKpp. [LHCb-CONF-2011-007, LHCb-CONF-2011-018]

– Other signals & work in progress.

B0DK- and fd/fs [LHCb-CONF-2011-013]Goals:I. Precise measurement of fs/fd. [ Very important for normalizing Bs decay rates in LHCb

] [1] Using BsDs

-p+ and B0D-K+

[2] Using BsDs-p+ and B0D-p+

Refer to talk by Neils Tuning on TuesdayII. Improve on B(B0D-K+) [Current error ~30%]

p

K

K

p

IP

Topology:E.g: BsDsp

D Daughters• IP c2 > 9, pT>300 MeV• DLL(K-p) < 10 (p)• DLL(K-p) > 0 (K)

Offline Selection: most notable:Bachelor• IP c2 > 9, pT>500 MeV• DLL(K-p) < 0 (p)• DLL(K-p) > 5 (K)

D • pT>1.5 GeV• Vertex c2/dof < 12

B • tB > 0.2 ps• Vertex c2/dof < 12

BDT used to optimize usage of a number ofkinematic variables: Trained on signal MC and data sidebands

Trigger: L0 & HLT must Trigger On Signal(TOS) B hadron

Bs

Ds

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Signals and ResultsB0 D-K+

YieldsB0 D-p+ 4109 ± 75B0 D-K+ 253 ± 21

Even

ts/8

MeV

Even

ts/1

6 M

eV

B0 D-p+

BDp faking BDK, shape derived from data

Most precise measurement of this branching fraction!

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First Observation of BsD0K*0

Ultimate goal is to use B0D0K*0 to measure g. Both diagrams are O(l3) & CS interference term large Flavor-specific time-independent analysis

But significant source of background from Bs D0K*0 , and is O(l2)

O(l2)

Immediate goal:Measure the rate of this process

Normalize to B0D0r0. Kinematically similar (most systematics cancel)

[LHCb-CONF-2011-008]

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Analysis Details

D0 Daughters, K (p)• IP c2 > 4• pT>400 (250) MeV• DLL(K-p) < 4 (p)• DLL(K-p) > 4 (K)

Offline Selection: most notable:

K*/r0 daughters• IP c2 > 4, pT>300 MeV• DLL(K-p) < 3 (p)• DLL(K-p) > 3 (K)

K* (r0)• pT > 1 GeV• |cosqh|>0.4• |m-mV|<50 (150) MeV

B • tB > 0.2 ps• Vertex c2/dof < 4• IP c2 to PV < 9

D0 • pT>1.5 GeV• Vertex c2/dof < 5• |m-mD|<20 MeV

p

K

p

Topology:E.g: BD0K*0

K(p)D0

B0 K*/r0

Uses both TOS and TIS events

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Observed SignalsB0 D0r0 Normalization Mode

Bs D0K*0 Signal Mode

Bs candidate mass (GeV)

Kp invariant mass (MeV)

pp invariant mass (MeV)

B0 candidate mass (GeV)

• Non-r0 contribution: Estimated to be: 30±8 events (need to subtract from the D0r0 yield)• Kp spectrum appears to be consistent with only K*

Yield

B0D0r0 154 ± 14

BsD0K*0 35 ± 7

First Observation

Results

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Using fd/fs = 3.71±0.47 from HFAG

0 0 *0

/0 0 0

( ) 1.39 0.31 0.17 0.18( ) d s

sstat syst f f

B B D KB B D r

PID systematic is conservative at this point.

XbXcppp & XbXcKpp Current measurements are of low precision, ≥ 30% uncertainty or non-existent

These multi-body decays are of interest: Bs Ds ppp for Dms and serves as a

calibration of SSKT for BsDsKpp . B0 D-ppp can be used to extract g. BsDsKpp for time-dep. g meas. B-D0Kpp for time-indep. g meas. Improve our understanding of B decays

Xb = B(s) or Lb Xc = D(s) or Lc

p

K

p

Topology:E.g: B D Kpp

KD

B K1(1270)

p K

• Similar selection criteria to previousanalyses: IP c2, pT, vertex c2, B “points” back to the PV, etc.

PDG

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Signals in CF modes

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Signal ModesB0 D-ppp B- D0ppp

Bs Dsppp Lb Lc ppp

B0 D-p B- D0p

Bs Dsp Lb Lc p

Normalization Modes

Only TOS events used for BF measurement.S/B in 5,6 body modes not much lower than in 3, 4 body modes

Sub-structure in the ppp spectrum

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Red points witherror bars show data

Line shows MC simulation

Significant a1(1260) +

component, but also longtail (non-resonant) out to 3 GeV

Similar structure for all b-hadron species.

B0 D-ppp B- D0ppp

Bs Dsppp Lb Lc ppp

Results

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Significant improvement in our knowledge of these decays

Interestingly, the B- D0ppp ratio is closer to 1.0, as opposed to 2.0? Both CF and CS diagrams present.

(Unlike B0, Bs or Lb) Strong phase(s) differ…

Systematics: ~10%Dominant: Tracking (2 tracks): 6% Trigger Efficiency: 5% Mass Fit: 4-6% All are reducible in near future

PDG

Two body amplitude analysis, see: Rosner and Chang, PRD67, 074013 (2003).

Cabibbo-Suppressed Decays

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Extension of the analysis on CF decays. Slightly tighter kinematic selections: applied to both signal and normalization mode

Take all triggers: Signal & trigger efficiencies ~equal to first order. Tighter kaon PID to suppress CF background; pK<100 GeV (effective region for K/p separation)

With 35 pb-1, we expect ~100 signals events (should be observable)

B0D-Kpp and B-D0Kpp

Selection & trigger efficiencies, as determined from signal MC

this is not surprising, as the kinematics are very similar.kin kinCS CFe e

0 0

0 0

1.08 0.04 1.04 0.03trig trigB D B Dtrig trigB D K B D K

ppp ppp

pp pp

e ee e

- -

- -

Slightly lower trigger efficiencyin CS mode due to pK<100 GeVrequirement

• Excludes kaon PID efficiency• Evaluated directly from D*

calibration data

Signals in Data

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B0D-Kpp B-D0Kpp

B0D- ppp B-D0ppp

First Observation

First Observation

6.6ssignificance

8.0ssignificance

Results on CS Decays

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For comparison: BDK:

Observed ratios in the range of what is expected.

Fitting uncertainty~5% dominantsystematic.

B mass signal region

B mass sideband region

Kpp mass spectrum consistent with dominance of lower lyingK** resonances

Other bbeautiful signals in key modes

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B- D0p-

With D0Kspp

With D0Kp With D0KK With D0pp

B- D0K-

Working toward g measurement in B- D0K-

With D0KsK+K-

Summary• CKM angle g is one of LHCb’s key measurements for exposing or

constraining new physics.

• With just 37 pb-1, we have already made world-class measurements.

• Yields in key channels are consistent with our expectations.– On track to carry out our rich program of CPV measurements.

• Several first observations … and more certainly to come.– Bs and Lb decays largely uncharted territory!

• With the 2011 data sample, (~1 fb-1) we expect to measure g to ~5-7o.

• We’re optimistic that theSM will yield to precisionb decay measurements!

2020

LHCb, with sg~5o

E. Lunghi and A. Soni arXiv.1010.6069v2

B0 D0r0

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(Triggered on Other B)(Triggered on Signal B)