Alexis POMPILI ( University & I.N.F.N. of Bari ) [representing the Collaboration]

Alexis POMPILI (University & I.N.F.N. of Bari)

[representing the Collaboration]

Les Rencontres de Physique de la Vallee d’Aoste La Thuile – March 3, 2004

CHARM PHYSICS

in

La Thuile - 2004 Alexis Pompili (U. of Bari &

I.N.F.N.)

2

Charm Physics @ BaBar - Outline

D0 mixing with 2-body hadronic decays (wrong sign & CP final states)

3-body decays of D0, D+, Ds+ ( B. R., Light Meson Spectroscopy, CP, mixing )

states spectroscopy sc

charmed baryons

Other Studies in progress:

ISR processes

][ )2458(),2317(*sJsJ DD

Analyses results reviewed here:

D0 mixing with semi-leptonic decays


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Charm Physics @ PEP-II B-factory

PEP-II (SLAC) : asymmetric e+e- collider @ Y(4S)

Integrated luminosity delivered : ~178fb-1

e+e- (nb) bb cc ss uu dd

1.05 1.30 0.35 1.39 0.35

+- +- e+e-

0.94 1.16 40

Powerful tool for charm physics

KDDD 00 ,*BABAR (90fb-1): ~220KFocus : 120KE791 : ~36K

Effective qq cross sections at the energy of the Y(4S)

][ 1 fbLdt

La Thuile - 2004 Alexis Pompili (U. of Bari & I.N.F.N.) 4

PID

TRACKING

VERTEXING

Crucial for

charm physics e+

e-

K-Id

DRIFT CHAMBER

SILICON VERTEX

The detector

CERENKOV DETECTOR

KAON EFFICIENCY

PION CONTAMINATION

CHERENKOV

][ cGeVplabReconstructed K-K+ Mass (GeV/c2)

KKD0


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Selecting charm decays from continuum

Kinematical selection: require cut on CMS

momentum of charmed meson : cGeVpD

5.2*(*)

π;π; 00

s** -cc-ee KDDDXD

combinatorial background strongly reduced

Refitting technique with beamspot - constraint

μm10

μm120

μm140μm70

allows flavor-tagging

improves m resolution

D*-TAG with S

D(*) from B-decays rejected

Beamspot

D*

D0

S

reduces BKGD through m = [m(K-+s) - m(K-+)]

6

D-mixing: parameters & search methods

Mass eigenstates: 1|||| 220002,1 ,||| qpDqDpD 00 |,| DD( flavour eigenstates)

masses: M1 , M2 widths: 1 , 2

MIXING PARAMETERS:

2, y

Mx

21

21

21

2/)(

MMM

310|y|,|x| SM

:NEW PHYSICS may enhance x

FSI & SU(3)-breaking can enhance y

beyond the reach of current experimental sensitivity …but

NP may not conserve CP consider CP when measuring mixing

Experimental goal : to put limits on the transition D0-D0

1) LIFETIME DIFFERENCE searches

2) WRONG-SIGN searches in hadronic decays

x2 , y ; : unknown strong phase difference

y [if CP conserved]

2,2)()(arg ff AApq

0|| DHfA Df0 pqmr 1mr

0

CP in mixing ( sure sign of NP )

CP in interference mixing–decay


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Lifetime difference searches

Mixing would alter the decay-time distributions of D0 and D0 that decay into CP eigenstates.They can be considered to a good approx. as pure exponential with effective lifetimes:

These effective lifetimes can be combined into:

AYY

00

,1

A

)(2

1 LIFETIME RATIO

IF NO MIXING : x = y = 0

IF CP-CONSERVATION IN MIXING : rm=1

0 0, YY

cosyY sinxY

for CFD

for CSD of D0 (D0) into CP-even

final states (such as K+K-,+-)

)( 00 KDKD

IF ALSO … CP-CONSERVATION IN INTERFERENCE MIXING -DECAY :0Y

yY 0sin

10 sincos(1 1 xyrm

where

Systematics effects on lifetime tend to cancel in the lifetime RATIO


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Mass fits

FROM THE FITS :

SIGNAL (S)

BKGD (B)

“sidebands”candidates included as part of proper time fit

BKGD constrained

in data

Mass fits determineevent-by-event

signal probability

DATA FIT RESULT

191 fb

~265K

~13K

~26K

~145K

99.4% 97.0%

87.9%68.1%

yield

S/S+B215 cMeV

mass window


Decay-time distributions fit

within mass signal window: 215 cMeV

FROM THE FITS :SIGNAL

BKGD

DATA UNBINNED MAXIMUM LIKELIHOOD FIT RESULT

D0 SAMPLES MEASURED QUANTITY MEASURED PARAMETER

K-K+ , -+ [CSD – CP-even]

K-+ [CF – CP-mixed] -

D*-untagged K-K+

A,0

YY ,

Y

,0


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Summary of lifetime ratio results [Phys.Rev.Lett.91,12(2003)]

BaBar has the most stringent limits on y

BaBar has the first measurement of a CPparameter with the method of lifetime ratio

191 fb

hep-ex/0308034

CS Sample Y(%) Y(%)

K-K+

-+

D*-untagged K-K+ -

Combined5.04.04.08.0

2.06.08.0

2.01.13.0

2.08.03.1 5.08.05.1

5.04.05.02.0

2.16.02.17.1

Wrong-sign searches in hadronic decays

DCSD & CFD may have different FSI

KK

KK

yxy

yxx

cossin

sincos

)(

)(0

0

KD

KDR

CF

DCS

D

Assuming and CP conservation :1, yx )0,1( mr

22220

4

1)()( tyxtRyRetKDt DDWS

twhere

01D

deviation from pure exponential

DCSD INTERFERENCE MIXING

222 yxRyRR DDWS Integrating :

enhances mixing signal

Additional CP effects are included by measuring this distribution for D0 and D0 separately:

mixing rate :

), ofrotation (,; yxRR

RRA

RR

RRA

MM

MMM

DD

DDD

CP in DCSD CP in MIXING CP in their INTERFERENCE11

K : unknown relative strong phase (not measurable in a mixing analysis): rotation of Kin the x-y plane :

MR

Study time-evolution of π0 KD looking for a signal π00 KDD

Mass-mass difference Fit

WS

m(K) m

Sideband

Signalregion

Assign each candidate to one of 4 categories: D0(RS,WS),D0(RS,WS)

Unbinned extended max-likelihood fit to RS and WS samples simultaneously in 4D variable space performed in steps :

Number of SIGNAL and BKGD candidates from a fit to m-m plane (both RS and WS) by modelling BKGD categories

With 57fb-1: ~120,000 RS ~ 440 WS

ttKmKmmKm S ,,)]()([,)(

1st step fit

Signal

Wrong slow pion

Double mis-id

Combinatorial


proper time error

Decay time Fit

Simultaneous fit time-distribution to RS and WS (include mixing parameters). The larger/clean RS sample fixes D0 lifetime and resolution model parameters for unmixed decays. BKGD time distributions determined from m,m sidebands in data.

WS

2nd step fit

Signal Wrong slow pion

Double mis-idCombinatorial


La Thuile - 2004 Alexis Pompili (U. of Bari & I.N.F.N.)

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Summary of wrong-sign results

(Prelim.)

[Phys.Rev.Lett.91,17(2003)]

WSR

95% C.L. contours by a frequentistic approach(based on toy Monte Carlo experiments) :

BEST FIT(x’2 free)

NO CPBEST FIT(x’2=0)

CP allowed

(stat.)

(stat.+syst.)

WSD RR

Results presented in 4 cases :


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Two surprising new Charmed Mesons : &)2317(*sJD

cGeVDp s 5.3)( 0*

MeV5.8

][)( 20 cGeVDm s

191 fb

[Phys.Rev.Lett. 90,24(2003)]

0)2112(* ss DD

)2458(sJD

BaBar observed a second new narrow state in the Ds*+ 0 invariant mass distribution near 2.46GeV/c2

! !

BaBar discovered a new narrow state in the Ds+ 0

invariant mass distribution near 2.32GeV/c2

[Accepted by P.R.L. ; hep/ex-0310050] cGeVDp s 5.3)( 0*

][)( 20 cGeVKKm

)( KKm )(m

]/[)( 2cGeVDm s

191 fb

sD

D

][)( 20 cGeVm ][)( 20 cGeVm

)()()( 00 ss DmDmm

0

sidebands 0sidebands sD

sidebandssubtraction

sidebands *sD

)2317(or through

decay tomay state This*0*

0

sJs

s

DD

D

CLEO observed them in continuum and… Belle both in continuum and in B decays [ ] *

sJDDB

Channel Likelihood Fit

16

To disentangle these 2 possible DsJ(2458) decay modes & extract signal parameters:unbinned maximum likelihood fit using the channel likelihood method

2.)(0.1.)(0.10.2458 cMeVsyststatm

2.)(8.0.)(4.03.2317 cMeVsyststatm

MeVstat.)(2.03.7

contribution from DsJ(2458) decays

combinatorial background

MeVstat.)(0.15.8

][)( 20 cGeVDm s][)( 20 cGeVDm s

26195

501022

230

.)(03.0.)(03.0250)]2317([

)]2458([syststat.

DR

DR*sJ

sJ

BELLE

CLEO

)2317(*sJD

)2458(sJD

)3.5GeV/c(in rate production lativeRe 2* pcc

0Belle][by )2458( JDD ssJ

Un-natural spin-parity more likely (lack of decays to DK)

Belle helicity analysis from B-decays favours J=1

Decay to Ds+- (by Belle) allowed by JP=1+

Decay to JP=0- mesons only natural spin-parity allowed [0+,1-,2+,…]

JP=0+ suggested by: 1) low mass compared to Ds1(2535) & DsJ*(2573) 2) absence of decay to Ds

+ (not allowed if JP=0+)

3) absence of decay to Ds++- (not allowed if JP=0+)

)2317(*sJD

)2458(sJD

SPIN-PARITY


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Two narrow states observed, in the inclusive Ds0 & Ds*0 invariant mass distributions, near 2.317GeV/c2 & 2.458GeV/c2.The widths [<10MeV] are consistent with experimental resolution. The most likely assignment for their spin-parity is 0+ & 1+.

EXPERIMENTALSUMMARY

Spectroscopy of states (before & after)

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Potential models of [heavy-quark | light-quark] mesons: so far reasonable success for spectroscopy of D, Ds, B, Bs systems

sc

P-waveS-wave)2573(*

sJD)2535(1sD)2112(*

sD)1969(sD

lightheavy SLjSjJ

,

011 S

131 S

)48.2(1 03P

)53.2(1 11P ?

?2

31 P

131 P

NEW STATES

DK

D*K

[j=3/2; NARROW by K-emission]

40(!) papers by theorists: Exotic (4-quark, molecule, …)

VSOrdinary explanations (HQET+chiral symmetry, …)

Crucial to measure radiative decays & di-pion emission

)2458(sJD

)2317(*sJD

New states do not fit well :masses below the DK[D*K] threshold.

A possible decay mechanism isthrough a virtual followed by -0 mixing [Cho-Wise,PRD49].

IF interpreted as ordinary states, theydecay mainly by isospin-violating -emission thus having widths quite narrow.

sc

)]2112([)]2458([

)]1969([)]2317([*

*

ssJ

ssJ

DmDm

DmDm

…as predicted by models based on HQET & chiral symmetry [Bardeen et al.,…] if new states are 0+ & 1+


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SUMMARY

wrong-sign D0 mixing limits (95% CL,57fb-1;CP-allowed):

D0 lifetime ratio (91fb-1):

Competitive D0 mixing results obtained with 2 different experimental methodsare consistent with no mixing and no CP.

Wrong-sign D0 mixing limits from semileptonic decays coming soon

0016.0,039.0056.0,0022.02 MRyx

)parameter CP(.)]%(2.0.)(6.08.0[

)conserved CP if(.)]%(.)(4.08.0[ 5.04.0

syststatY

ysyststatY

After the discovery of D*sJ(2317) and the observation of DsJ(2458)…

… further Ds mesons (spectroscopic) studies are ongoing.

BaBar is a promising place to study charm physics … studies have just began !

Charmed mesons are a rich laboratory for Heavy Quark studies.

Backup Slides

La Thuile - 2004 A.Pompili (U. of Bari &

I.N.F.N.) BACKUP-1

Unbinned maximum likelihood fit

)parametersδt;,t,(where 11imiPiPiL

[1Psig(mi

)]

Psig(mi

) SIGNAL

BKG

proper-time RESOLUTION

(1-f2)(1-f3) + f2(1-f3) + f3

S1 S2 3

f0f4

4 fixed

(1-f0) + f0(1-f4)

NO-flying BKG

flying BKG

BUT with ...

for tails

SBKG S1

SBKG S2

3

BKG

D

Statistical error on lifetime extracted from the fit


I.N.F.N.) BACKUP-2


I.N.F.N.) BACKUP-3

Fit allowed x’2<0.Central values for fits of both separate samples gave x’2<0.

95% C.L. limits are determinedusing toy Monte Carlo samplesat each point on the contour(frequentistic approach).

Due to allowing x’2<0 in the fits it is not clear how to apply a Bayesian ansatz to derive an error estimate from the 2D likelihood distributions. Moreoverthese ones depend strongly on themost likely fitted values of x’2 and y.

(x’2,y) points on separate contours are combined in pairs to determine (x’2,y) on 95% CP contours.

Systematic uncertainties included by calculatingequivalent statistical deviation for each systematic check and expanding the 95% C.L. contour appropriately.


I.N.F.N.) BACKUP-4


I.N.F.N.) BACKUP-5

Unbinned maximum likelihood fit

Assign likelihood to each event for:

– DsJ(2458)+ Ds*(2112)+ 0

– DsJ(2458)+ DsJ*(2317)+

– Combinatorial Ds+ 0 bkgd

– Ds*(2112)+ + random 0

– DsJ*(2317)+ + random

– DsJ(2458)+ Ds*(2112)+ 0

… using wrong

The DsJ(2458) signal for a particular decay mode can be isolated by calculating a weight for each

Ds0 combination proportional to the relative likelihood contributed by the decay mode of

interest

Alexis POMPILI ( University & I.N.F.N. of Bari ) [representing the Collaboration]

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Transcript of Alexis POMPILI ( University & I.N.F.N. of Bari ) [representing the Collaboration]