Bs DsK and B DK States
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Transcript Bs DsK and B DK States
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
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 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.
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. BsDs+K-, BsDs±K-p+pB0D-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
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 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.
5
B0DK- 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 BsDs-p+ and B0D-K+
[2] Using BsDs-p+ and B0D-p+
Refer to talk by Neils Tuning on Tuesday
Improve on B(B0D-K+) [Current error ~30%]
Offline Selection: most notable:
D Daughters
c2
IP
p
Bs
Ds
Topology:
E.g: BsDsp
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
BDp faking BDK,
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 BsD0K*0
Ultimate goal is to use B0D0K*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 B0D0r0.
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: BD0K*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)
B0D0r0
154 ± 14
BsD0K*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
XbXcppp & XbXcKpp
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 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
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)
B0D-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
B0D-Kpp
B-D0Kpp
First
Observation
8.0s
significance
6.6s
significance
B0D- ppp
B-D0ppp
17
Results on CS Decays
Fitting uncertainty
~5% dominant
systematic.
For comparison: BDK:
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 D0Kp
With D0KK
With
D0Kspp
With D0pp
B- D0K-
With
D0KsK+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
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B0 D0r0
(Triggered on Signal B)
(Triggered on Other B)
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