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BsDsh and BDh Decays in LHCb

Steven Blusk

Syracuse 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. 2-3 deviations in sin(2)

Large direct CPV in BK. Maybe hints in sin(2s), 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 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 in LHCb• Time-independent (ADS, GLW, GGSZ, etc)

– E.g. B- D0K- B0 D0K*0 B- D0K-+-

• Time-dependent – E.g. BsDs

+K-, BsDs±K-+-

B0D-+ B0D-++

• Challenges:– Sensitivity through bu low rates– Excellent PID critical, e.g. DCS D0K– Fully hadronic mode, triggering,

backgrounds

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

analysis)– Trigger: next slide

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

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

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

• Hlt1/off-selxL0 ~ 80-90%– HLT2: Form 2, 3, and 4-body states, among tracks with IP 2>16,

pT>0.5 GeV, p>5 GeV. • Hlt2/off-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 XbXc and First observation of BDK. [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- and B0D-K+

[2] Using BsDs- and B0D-+

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

K

K

IP

Topology:E.g: BsDs

D Daughters• IP 2 > 9, pT>300 MeV• LL(K-) < 10 ()• LL(K-) > 0 (K)

Offline Selection: most notable:

Bachelor• IP 2 > 9, pT>500 MeV• LL(K-) < 0 ()• LL(K-) > 5 (K)

D • pT>1.5 GeV• Vertex 2/dof < 12

B • B > 0.2 ps• Vertex 2/dof < 12

B • B > 0.2 ps• Vertex 2/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+

Yields

B0 D-+ 4109 ± 75

B0 D-K+ 253 ± 21

Ev

en

ts/8

Me

VE

ve

nts

/16

Me

V

B0 D-+

BD 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 . Both diagrams are O(3) & CS interference term large Flavor-specific time-independent analysis

But significant source of background from Bs D0K*0 , and is O(2)

O(2)

Immediate goal:Measure the rate of this process

Normalize to B0D00. Kinematically similar (most systematics cancel)

[LHCb-CONF-2011-008]

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Analysis Details

D0 Daughters, K ()• IP 2 > 4• pT>400 (250) MeV• LL(K-) < 4 ()• LL(K-) > 4 (K)

Offline Selection: most notable:

K*/0 daughters• IP 2 > 4, pT>300 MeV• LL(K-) < 3 ()• LL(K-) > 3 (K)

K* (0)• pT > 1 GeV• |cosh|>0.4• |m-mV|<50 (150) MeV

B • B > 0.2 ps• Vertex 2/dof < 4• IP 2 to PV < 9

B • B > 0.2 ps• Vertex 2/dof < 4• IP 2 to PV < 9

D0 • pT>1.5 GeV• Vertex 2/dof < 5• |m-mD|<20 MeV

K

Topology:E.g: BD0

K()D0

B0K*/0

Uses both TOS and TIS events

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Observed SignalsB0 D00 Normalization Mode

Bs D00 Signal Mode

Bs candidate mass (GeV)

K invariant mass (MeV)

invariant mass (MeV)

B0 candidate mass (GeV)

• Non-0 contribution: Estimated to be: 30±8 events (need to subtract from the D00 yield)• K spectrum appears to be consistent with only K*

Yield

B0D00 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 K

B B D

PID systematic is conservative at this point.

XbXcXbXcK Current measurements are of low precision, ≥ 30% uncertainty or non-existent

These multi-body decays are of interest: Bs Ds for ms and serves as a calibration of SSKT for BsDsK . B0 D- can be used to extract . BsDsK for time-dep. meas. B-D0K for time-indep. meas. Improve our understanding of B decays

Xb = B(s) or b Xc = D(s) or c

K

Topology:E.g: B D K

D

B K1(1270)

K

•Similar selection criteria to previousanalyses: IP 2, pT, vertex 2, B “points” back to the PV, etc.

PDG

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Signals in CF modes

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Signal Modes

B0 D- B- D0

Bs Ds b c

B0 D- B- D0

Bs Ds b c

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 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- B- D0

Bs Ds b c

Results

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Significant improvement in our knowledge of these decays

Interestingly, the B- D0 ratio is closer to 1.0, as opposed to 2.0?

Both CF and CS diagrams present. (Unlike B0, Bs or b) 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/ separation)

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

B0D-KandB-D0K

Selection & trigger efficiencies, as determined from signal MC

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

0 0

0 0

1.08 0.04 1.04 0.03trig trig

B D B Dtrig trig

B D K B D K

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-KB-D0K

B0D- B-D0

First Observation

First Observation

6.6significance

8.0significance

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

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

Other bbeautiful signals in key modes

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B- D0-

With D0Ks

With D0K With D0KK With D0

B- D0-

Working toward measurement in B- D0K-

With D0KsK+K-

Summary• CKM angle 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 b decays largely uncharted territory!

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

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

2020

LHCb, with ~5o

E. Lunghi and A. Soni arXiv.1010.6069v2

B0 D00

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