Transcript Bs DsK and B DK States

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
1
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
E. Lunghi and A. Soni arXiv.1010.6069v2
 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.
2
Angle g in LHCb
• Time-independent (ADS, GLW, GGSZ, etc)
– E.g. B-  D0KB0  D0K*0
B-  D0K-p+p• Time-dependent
– E.g. BsDs+K-, BsDs±K-p+pB0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
3
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%
•
eHlt2/eoff-selxHlt1xL0 ~ 80-90%
– HLT2: Form 2, 3, and 4-body states, among tracks with IP c2>16,
pT>0.5 GeV, p>5 GeV.
• 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
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-2011-013]
– First observation of BsD0K*0 [LHCb-CONF-2011-008]
– New measurements of XbXcppp and First observation of
BDKpp. [LHCb-CONF-2011-007, LHCb-CONF-2011-018]
– Other signals & work in progress.
5
B0DK- and fd/fs [LHCb-CONF-2011-013]
Goals:
I.
II.
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
c2
IP
p
Bs
Ds
Topology:
E.g: BsDsp
K
K
• IP > 9, pT>300 MeV
• DLL(K-p) < 10 (p)
• DLL(K-p) > 0 (K)
D
• pT>1.5 GeV
• Vertex c2/dof < 12
Bachelor
• IP c2 > 9, pT>500 MeV
• DLL(K-p) < 0 (p)
• DLL(K-p) > 5 (K)
B
• tB > 0.2 ps
• Vertex c2/dof < 12
p
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
B0

Signals and Results
D-K+
Events/16
MeV
Events/8MeV
BDp faking BDK,
shape derived from data
Yields
B0  D-p+
4109 ± 75
B0  D-K+
253 ± 21
B0  D-p+
Most precise measurement
of this branching fraction!
7
First Observation of BsD0K*0
 Ultimate goal is to use B0D0K*0 to measure g.
[LHCb-CONF-2011-008]
 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)
Immediate goal:
Measure the rate of this process
O(l2)
Normalize to B0D0r0.
Kinematically similar
(most systematics cancel)
8
Analysis Details
Offline Selection: most notable:
D0 Daughters, K (p)
B0
• IP c2 > 4
• pT>400 (250) MeV
• DLL(K-p) < 4 (p)
• DLL(K-p) > 4 (K)
• IP c2 > 4, pT>300 MeV
• DLL(K-p) < 3 (p)
• DLL(K-p) > 3 (K)
K*/r0
p
D0
Topology:
E.g: BD0K*0
K*/r0 daughters
K(p)
K
p
D0
K* (r0)
• pT>1.5 GeV
• Vertex c2/dof < 5
• pT > 1 GeV
• |cosqh|>0.4
• |m-mV|<50 (150) MeV
• |m-mD|<20 MeV
B
• tB > 0.2 ps
• Vertex c2/dof < 4
• IP c2 to PV < 9
Uses both TOS and TIS events
9
Observed Signals
B0  D0r0 Normalization Mode
First
Observation
Bs  D0K*0 Signal Mode
B0 candidate mass (GeV)
Bs candidate mass (GeV)
Yield
pp invariant mass (MeV)
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*
10
Results
Using fd/fs = 3.71±0.47 from HFAG
B( Bs0  D0 K *0 )
 1.39  0.31stat  0.17 syst  0.18 f d / f s
0
0 0
B( B  D r )


PID systematic is
conservative at this
point.
11
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
B
Topology:
E.g: B D Kpp
•Similar selection criteria to previous
analyses: IP c2, pT, vertex c2, B “points”
back to the PV, etc.
K1(1270)
D
PDG
K
p
K
p
p
K
12
Signals in CF modes
Signal Modes
B0 D-ppp
Bs Dsppp
B- D0ppp
Lb  Lc ppp
Normalization Modes
B0 D-p
Bs Dsp
Only TOS events used for BF measurement.
S/B in 5,6 body modes not much lower than in 3, 4 body modes
B- D0p
Lb  Lc p
13
Sub-structure in the ppp spectrum
B0 D-ppp
B- D0ppp
Red points with
error bars show data
Line shows MC simulation
Bs Dsppp
Lb  Lc ppp
Significant a1(1260) +
component, but also long
tail (non-resonant) out to
3 GeV
Similar structure for all
b-hadron species.
14
Results
Systematics: ~10%
Dominant:
Tracking (2 tracks): 6%
Trigger Efficiency: 5%
Mass Fit:
4-6%
 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, 074013 (2003).
15
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
kin
kin
e CS
 e CF
e Btrig D ppp
 1.08  0.04 
trig
e B  D Kpp
0
-
0
-
this is not surprising, as the kinematics are very similar.
e Btrig D ppp
 1.04  0.03
trig
e B  D Kpp
-
0
-
0
Slightly lower trigger efficiency
in CS mode due to pK<100 GeV
requirement
16
First
Observation
Signals in Data
B0D-Kpp
B-D0Kpp
First
Observation
8.0s
significance
6.6s
significance
B0D- ppp
B-D0ppp
17
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
18
Other bbeautiful signals in key modes
Working toward g measurement in B-  D0K-
B- D0p-
With D0Kp
With D0KK
With
D0Kspp
With D0pp
B- D0K-
With
D0KsK+K-
19
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!
LHCb, with sg~5o
• 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!
E. Lunghi and A. Soni arXiv.1010.6069v2
20
B0 D0r0
(Triggered on Signal B)
(Triggered on Other B)
21