1. BsDsh and BDh Decays in LHCb
Steven Blusk
Syracuse University
On behalf of the LHCb Collaboration
Beauty 2011, Amsterdam, The Netherlands, April 4-8, 2011

2. Introduction
If NP exists, (and its couplings to the quark sector are not highly suppressed), there should be observable/sizeable effects in loop-mediated diagrams.
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 BKp.
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.
E. Lunghi and A. Soni arXiv v2

3. Angle g in LHCb Time-independent (ADS, GLW, GGSZ, etc)
E.g. B-  D0K B0  D0K* B-  D0K-p+p-
Time-dependent
E.g. BsDs+K-, BsDs±K-p+p B0D-p B0D-p+p-p+
Challenges:
Sensitivity through bu low rates
Excellent PID critical, e.g. DCS D0Kp
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

4. 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

5. 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 B0DK- [LHCb-CONF ]
First observation of BsD0K*0 [LHCb-CONF ]
New measurements of XbXcppp and First observation of BDKpp. [LHCb-CONF , LHCb-CONF ]
Other signals & work in progress.

6. B0DK- and fd/fs [LHCb-CONF-2011-013]
Goals:
Precise measurement of fs/fd. [ Very important for normalizing Bs decay rates in LHCb ]
[1] Using BsDs-p+ and B0D-K+
[2] Using BsDs-p+ and B0D-p+
Refer to talk by Neils Tuning on Tuesday
Improve on B(B0D-K+) [Current error ~30%]
Offline Selection: most notable:
D Daughters
IP c2 > 9, pT>300 MeV
DLL(K-p) < 10 (p)
DLL(K-p) > 0 (K)
Bachelor
IP c2 > 9, pT>500 MeV
DLL(K-p) < 0 (p)
DLL(K-p) > 5 (K) p K IP
Topology: E.g: BsDsp Bs Ds D
pT>1.5 GeV
Vertex c2/dof < 12 B
tB > 0.2 ps
Vertex c2/dof < 12
a1 gives the deviation from naïve factorization
F0 are the form factors at the given q^2
BDT used to optimize usage of a number of kinematic variables:
 Trained on signal MC and data sidebands
Trigger: L0 & HLT must Trigger On Signal (TOS) B hadron

7. Most precise measurement of this branching fraction!
Signals and Results
B0  D-K+
BDp faking BDK, shape derived from data
Events/8 MeV
Events/16 MeV
Yields
B0  D-p+
4109 ± 75
B0  D-K+
253 ± 21
B0  D-p+
Most precise measurement of this branching fraction!

8. First Observation of BsD0K*0
Ultimate goal is to use B0D0K*0 to measure g.
Both diagrams are O(l3) & CS  interference term large
Flavor-specific  time-independent analysis
[LHCb-CONF ]
But significant source of background from Bs D0K*0 , and is O(l2)
Immediate goal: Measure the rate of this process
Normalize to B0D0r0.
Kinematically similar (most systematics cancel)
O(l2)

9. Analysis Details Offline Selection: most notable: D0 K* (r0) B
D0 Daughters, K (p)
IP c2 > 4
pT>400 (250) MeV
DLL(K-p) < 4 (p)
DLL(K-p) > 4 (K)
K*/r0 daughters
IP c2 > 4, pT>300 MeV
DLL(K-p) < 3 (p)
DLL(K-p) > 3 (K) p K
Topology: E.g: BD0K*0
K(p) D0 B0
K*/r0 D0
pT>1.5 GeV
Vertex c2/dof < 5
|m-mD|<20 MeV
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
Uses both TOS and TIS events

10. Observed Signals First Observation B0  D0r0 Normalization Mode
Bs  D0K*0 Signal Mode
B0 candidate mass (GeV)
pp invariant mass (MeV)
Bs candidate mass (GeV)
Yield
B0D0r0
154 ± 14
BsD0K*0
35 ± 7
Kp invariant mass (MeV)
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*

11. Results Using fd/fs = 3.71±0.47 from HFAG
PID systematic is conservative at this point.

12. XbXcppp & XbXcKpp Xb = B(s) or Lb Xc = D(s) or Lc
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 BsDsKpp .
B0 D-ppp can be used to extract g.
BsDsKpp for time-dep. g meas.
B-D0Kpp for time-indep. g meas.
Improve our understanding of B decays
PDG
Similar selection criteria to previous analyses: IP c2, pT, vertex c2, B “points” back to the PV, etc. B
K1(1270) K D p
Topology: E.g: B D Kpp K p p K

13. Signals in CF modes Signal Modes Normalization Modes
B0 D-ppp
B- D0ppp
B0 D-p
B- D0p
Bs Dsppp
Lb  Lc ppp
Bs Dsp
Lb  Lc p
Only TOS events used for BF measurement.
S/B in 5,6 body modes not much lower than in 3, 4 body modes

14. Sub-structure in the ppp spectrum
B0 D-ppp
B- D0ppp
Red points with error bars show data
Line shows MC simulation
Significant a1(1260) + component, but also long tail (non-resonant) out to 3 GeV
Similar structure for all b-hadron species.
Bs Dsppp
Lb  Lc ppp

15. Results PDG Significant improvement in our knowledge of these decays
Systematics: ~10%
Dominant:
Tracking (2 tracks): 6%
Trigger Efficiency: 5%
Mass Fit: %
 All are reducible in near future
PDG
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…
Two body amplitude analysis, see: Rosner and Chang, PRD67, (2003).

16. Cabibbo-Suppressed Decays
With 35 pb-1, we expect ~100 signals events (should be observable)
B0D-Kpp and B-D0Kpp
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)
Selection & trigger efficiencies, as determined from signal MC
Excludes kaon PID efficiency
Evaluated directly from D* calibration data
this is not surprising, as the kinematics are very similar.
Slightly lower trigger efficiency in CS mode due to pK<100 GeV requirement

17. Signals in Data B0D-Kpp B-D0Kpp B0D- ppp B-D0ppp First Observation
8.0s significance
6.6s significance
B0D- ppp B-D0ppp

18. Results on CS Decays Fitting uncertainty ~5% dominant systematic.
For comparison: BDK:
Observed ratios in the range of what is expected.
B mass signal region
B mass sideband region
Kpp mass spectrum consistent with dominance of lower lying K** resonances

19. Other bbeautiful signals in key modes
Working toward g measurement in B-  D0K-
B- D0p-
With D0Kp
With D0KK
With D0pp
With D0Kspp
B- D0K-
With D0KsK+K-

20. 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 the SM will yield to precision b decay measurements!
LHCb, with sg~5o 20
E. Lunghi and A. Soni arXiv v2

21. B0 D0r0
(Triggered on Signal B)
(Triggered on Other B)