3i-2 cowan recent babar charm physics...
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Recent BABAR Charm Physics ResultsRay F. Cowan
M.I.T.Representing the BABAR CollaborationRepresenting the BABAR Collaboration
PANIC 11
OutlineOutline
• The BaBar detector and datasetThe BaBar detector and dataset
• Search for CPV in D +Ksπ+
S h f C i dd l i i f• Search for CPV in T‐odd correlations in four‐body charm decays
• Dalitz plot analysis of D+s K+K−π+
• Mass and width of the Ds1(2536)+s1( )
• Searches for non‐hadronic rare D decays – D0 γγ– D γγ
25 July 2011 2Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
The BaBar detector at PEP‐IIThe BaBar detector at PEP II
NIM A479, 1 (2002)NIM A479, 1 (2002)
25 July 2011 3Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
DatasetDataset• PEP‐II at SLAC is not only a B
factory but also a charm factory 470 x 106 B anti B pairs– 470 x 106 B anti‐B pairs
– 690 x 106 c anti‐c pairs– 500 x 106 τ+τ− pairs
25 July 2011 4Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
CP violation in D decays with a K0SCP violation in D decays with a K S
• Standard model CPV arises from the Kobayashi‐Maskawaphase in the CKM matrix
Ch• Charm mesons– CP violation (CPV) is GIM suppressed, O(10−3)– Occurrence of a K0S introduces CPV of (0.332±0.006)% from
K0/ ti K0 i iK0/anti‐K0 mixing– Experimental sensitivity is O(10−3)– New physics would be indicated by a 1% signal
25 July 2011 5Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
Search for CPV in D ±K π+Search for CPV in D KsπPRD‐RC 83 071103 (2011)
• Direct CPV in Ks decays contributes– New physics effects could reduce or enhance
this effect• Uses new data‐driven method to determine
charge asymmetry in track reconstruction– Use of tracks from e+e− Y(4S) B anti‐B– Avoids any physics‐induced charge asymmetry– Corrections applied to D yields
800K signal eventsSolid line: signal; Dashed: reflection bkgDotted: combinatoric bkg
Ratio of π+/π− detection efficiencies (top)
469 fb‐1
Error on ratio (bottom)
25 July 2011 6Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
Search for CPV in D ±K π±Search for CPV in D Ksπ• Measure
• CPV asymmetry measured in bins of polar angle cos θ* in CMS
• Forward‐backward asymmetry from electroweak γ‐Z interference
• Result
– Consistent with SM prediction (‐0.332 ± 0.006)%
PRD 83 071103 (2011)
25 July 2011 7Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
Search for CPV in T‐odd correlations in four‐body charm decaysbody charm decays
• Measure a T‐odd observable– If CPT is conserved, then T‐violation
implies CPVimplies CPV
• Use D+(s) K+Ksπ+π− decays
• Define T‐odd observable for D(s)+
• And for D(s)−
• Define asymmetries
• Remove FSI effects using T‐odd variable
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T‐odd observables in D+(s) K+Ksπ+π− decays
• Reconstruct D±(s)
inclusively• p*(D) > 2.5 GeV/c• Use sidebands to
t i b k dparametrize backgrounds• Binned maximum‐
likelihood fit• Bkg model: 1st order poly
(D±); 2nd order poly (D±s)
• Signal model: 2 Gaussians with common mean
• 20,000 D±; 30,000 D±s
Systematics (x 10‐3)
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 9
T‐odd observables in D+(s) K+Ksπ+π− decays
• Results
• T violation parameters are consistent with zero
Arxiv:1105.4410 (hep‐ex)Submitted to PRD RCconsistent with zero Submitted to PRD‐RC
FOCUS: PL B622, 239 (2005)• And a factor of 10 smaller
uncertainties than previous result• Similar to BaBar analysis for D0
K+K−π+π−
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PRD 81, 111103 (2010)
Dalitz plot analysis of D+ K+K−π+Dalitz plot analysis of D s K K π
• Questions remain regarding light scalar mesonsg g g– Are a0(980) and f0(980) four‐quark states?
N d b d d KK• Need to better understand KK s‐wave– Also needed for precise CPV studies in Bs oscillations using BsJ/ψφg s /ψφ
• Study using D*s(2112) D+sγ, D+
s K+K−π+
– Partial wave analysis yields a model‐independent description of the KK s‐wave
• Complements our earlier ππ s‐wave analysisComplements our earlier ππ s wave analysis
25 July 2011 11Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
Dalitz plot analysis of D+s K+K−π+
• Select events using– p*(D+
s)>2.5 GeV/c, – Δm = m(KKπγ) − m(KKπ)
SignalBackground
– and three kinematic variables combined into one likelihood ratio
• Use Legendre moments to• Use Legendre moments to separate S and Pcontributions
Then parameterize the f0(980):
25 July 2011 12Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA
Dalitz plot analysis of D+s K+K−π+
• Dalitz fit model– fsig : signal fraction– η : efficiencies– ci: ampl. of fitted signal i
component I– x,y: KK, Kπmass2
– Ai, Bj : signal & background PDF contributions
– IX: normalization integrals– ki: magnitude of ith background
componentcomponent• Use of model‐independent
background removes uncertainties from coupling constants in previous analyses
• Gives a better description of the l l d h l fDalitz plot and the total fit
fractionsPRD 83, 052001 (2011)
D li fi j i
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Dalitz fit projections
Mass and width of the Ds1(2536)+• D masses and widths are not in good agreement with HQET• Dsj masses and widths are not in good agreement with HQET
• Alternative explanations include D*K molecules, chiral partners, unitarizedchiral models, tetraquarks, and LQCD, q , Q
• This result is the first precise measurement of the Ds1(2536)+ mass– First ever measurement of Ds1(2536)+ width
• Uses the decay modes m(D0) Δm m(KS)
Kπ
Kπππ
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 14
Mass and width of the Ds1(2536)+• Fit Δm = m(Ds1(2536)+) −
m(D*+)• Relativistic Breit‐Wigner plus
resolution function– Result
m(D 1(2536)+) = 2535.08±0.01±0.15 MeV/c2
Angular analysis( )
m(Ds1(2536) ) 2535.08±0.01±0.15 MeV/cΓ(Ds1(2536)+) ) = 0.92±0.03±0.04 MeV/c2
Distribution of Ds1(2536)+ to D0 helicity angle (left) and to D* helicity angle (right)
fi JP 1+confirms JP = 1+
Dash‐dotted line: constant;Solid line: (sin2θ’+βcos2θ’);
h d li 2θ’
Dotted line: constant;Solid line: (1+tcos2θ)
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 15
Dashed line: cos2θ’;Dotted line: sin2θ’
Rare Decays: D0 γγRare Decays: D γγ• FCNC: GIM‐suppressed loop diagrams in
charm sectorh l b• Short‐ and long‐distance contributions predicted to be at least O(102) below current experimental sensitivity
• Standard model is dominated by long‐di t t ib tidistance contributions
– PRD 66, 014009 (2002) • New physics could enhance the rate
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 16
D0 γγ• BaBar preliminary
– 407.5 fb‐1
• Dominant background D0 π 0π00π0
• Normalize to D0 Ksπ0 mode– Eliminates or reduces several
systematic uncertainties
Comb bkgComb bkg + D0 π0π0
Comb bkg + D0 π0π0 + signaldatadata
BABARlpreliminary
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 17
Summary• Search for CPV in D ±Ksπ±
– Consistent with zero and with Standard Model prediction• T‐odd observables in D+
(s) K+Ksπ+π− decays(s) s y– T violation parameters are consistent with zero– Uncertainties 10x smaller than previous result
• Partial wave & Dalitz plot analysis of D+s K+K−π+
– Yields model‐independent KK s‐wave description– Improved Dalitz plot description and total fit fractions
• Precision mass and width of Ds1(2536)+– m(Ds1(2536)+) = 2535.08±0.01±0.15 MeV/c2– Γ(Ds1(2536)+) ) = 0.92±0.03±0.04 MeV/c2– First precision measurement of the mass
Fi t t f th idth– First ever measurement of the width• Rare decay D0 γγ
– B(D0 γγ) < 2.4 x 10‐6
10x lower than PDG value– 10x lower than PDG value
25 July 2011 Ray Cowan — Recent BABAR Charm Physics Results — PANIC11 —MIT, Cambridge, MA USA 18