CHARM PHYSICS in Alexis POMPILI University I N

CHARM PHYSICS in 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 @ Ba. Bar - Outline Analyses results reviewed here: D 0 mixing with 2 -body hadronic decays (wrong sign & CP final states) states spectroscopy Other Studies in progress: D 0 mixing with semi-leptonic decays 3 -body decays of D 0, D+, Ds+ ( B. R. , Light Meson Spectroscopy, CP, mixing ) charmed baryons ISR processes La Thuile - 2004 2 Alexis Pompili (U. of Bari & I. N. F. N. )

Charm Physics @ PEP-II B-factory PEP-II (SLAC) : asymmetric e+e- collider @ Y(4 S) Integrated luminosity delivered : ~178 fb-1 Effective qq cross sections at the energy of the Y(4 S) Powerful tool for charm physics BABAR (90 fb-1): ~220 K Focus : 120 K E 791 : ~36 K La Thuile - 2004 3 Alexis Pompili (U. of Bari & I. N. F. N. )

The Crucial for charm physics PID detector CERENKOV DETECTOR TRACKING VERTEXING e+ DRIFT CHAMBER SILICON VERTEX e- KAON EFFICIENCY K-Id CHERENKOV Reconstructed K-K+ Mass (Ge. V/c 2) La Thuile - 2004 4 PION CONTAMINATION Alexis Pompili (U. of Bari & I. N. F. N. )

Selecting charm decays from continuum Kinematical selection: require cut on CMS momentum of charmed meson : combinatorial background strongly reduced D(*) from B-decays rejected D*-TAG with p. S allows flavor-tagging reduces BKGD through dm = [m(K-p+ps) - m(K-p+)] D 0 Refitting technique with beamspot - constraint D* improves dm resolution La Thuile - 2004 p. S Beamspot 5 Alexis Pompili (U. of Bari & I. N. F. N. )

D-mixing: parameters & search methods Mass eigenstates: ( masses: M 1 , M 2 widths: G 1 , G 2 MIXING PARAMETERS: SM : flavour eigenstates) beyond the reach of current experimental sensitivity …but NEW PHYSICS may enhance x FSI & SU(3)-breaking can enhance y Experimental goal : to put limits on the transition D 0 -D 0 1) LIFETIME DIFFERENCE searches 2) WRONG-SIGN searches in hadronic decays NP may not conserve CP y [if CP conserved] x 2 , y ; d: unknown strong phase difference consider CP when measuring mixing CP in mixing ( sure sign of NP ) 6 CP in interference mixing–decay

Lifetime difference searches Mixing would alter the decay-time distributions of D 0 and D 0 that decay into CP eigenstates. They can be considered to a good approx. as pure exponential with effective lifetimes: for CSD of D 0 (D 0) into CP-even final states (such as K+K-, p+p-) for CFD LIFETIME RATIO These effective lifetimes can be combined into: where IF NO MIXING : x = y = 0 IF CP-CONSERVATION IN MIXING : rm=1 IF ALSO … CP-CONSERVATION IN INTERFERENCE MIXING -DECAY : Systematics effects on lifetime tend to cancel in the lifetime RATIO La Thuile - 2004 7 Alexis Pompili (U. of Bari & I. N. F. N. )

Mass fits DATA ~265 K ~26 K 99. 4% 97. 0% FIT RESULT SIGNAL (S) FROM THE FITS : yield BKGD (B) S/S+B mass window ~145 K ~13 K 68. 1% Mass fits determine event-by-event signal probability 87. 9% “sidebands”candidates included as part of proper time fit La Thuile - 2004 8 Alexis Pompili BKGD constrained in data (U. of Bari & I. N. F. N. )

Decay-time distributions fit within mass signal window: SIGNAL FROM THE FITS : DATA D 0 SAMPLES BKGD UNBINNED MAXIMUM LIKELIHOOD FIT RESULT MEASURED QUANTITY MEASURED PARAMETER K-K+ , p-p+ [CSD – CP-even] K- p+ La Thuile - 2004 9 [CF – CP-mixed] - D*-untagged K-K+ Alexis Pompili (U. of Bari & I. N. F. N. )

Summary of lifetime ratio results CS Sample [Phys. Rev. Lett. 91, 12(2003)] DY(%) K- K+ p- p+ D*-untagged K-K+ - Combined hep-ex/0308034 Ba. Bar has the most stringent limits on y Ba. Bar has the first measurement of a CP parameter with the method of lifetime ratio La Thuile - 2004 10 Alexis Pompili (U. of Bari & I. N. F. N. )

Wrong-sign searches in hadronic decays Study time-evolution of DCSD & CFD may have different FSI Assuming looking for a signal d. Kp : unknown relative strong phase (not measurable in a mixing analysis): rotation of d. Kp in the x-y plane : and CP conservation : where deviation from pure exponential DCSD INTERFERENCE MIXING enhances mixing signal Integrating : mixing rate : Additional CP effects are included by measuring this distribution for D 0 and D 0 separately: 11 CP in DCSD CP in MIXING CP in their INTERFERENCE

Mass-mass difference Fit Assign each candidate to one of 4 categories: D 0(RS, WS), D 0(RS, WS) Unbinned extended max-likelihood fit to RS and WS samples simultaneously in 4 D variable space performed in steps : proper time error 1 st step fit m(Kp) Number of SIGNAL and BKGD candidates from a fit to m-dm plane (both RS and WS) by modelling BKGD categories dm Signal region Signal WS Wrong slow pion Combinatorial Double mis-id Sideband With 57 fb-1: ~120, 000 RS ~ 440 WS La Thuile - 2004 12 Alexis Pompili (U. of Bari & I. N. F. N. )

Decay time Fit 2 nd step fit Simultaneous fit time-distribution to RS and WS (include mixing parameters). The larger/clean RS sample fixes D 0 lifetime and resolution model parameters for unmixed decays. BKGD time distributions determined from m, dm sidebands in data. WS Signal Combinatorial La Thuile - 2004 13 Wrong slow pion Double mis-id Alexis Pompili (U. of Bari & I. N. F. N. )

Summary of wrong-sign results 95% C. L. contours by a frequentistic approach (based on toy Monte Carlo experiments) : BEST FIT (x’ 2 free) NO CP BEST FIT (x’ 2=0) [Phys. Rev. Lett. 91, 17(2003)] Results presented in 4 cases : (stat. +syst. ) (stat. ) (Prelim. ) CP allowed La Thuile - 2004 14 Alexis Pompili (U. of Bari & I. N. F. N. )

Two surprising new Charmed Mesons : & [Phys. Rev. Lett. 90, 24(2003)] Ba. Bar discovered a new narrow state in the Ds+ p 0 invariant mass distribution near 2. 32 Ge. V/c 2 ! ! [Accepted by P. R. L. ; hep/ex-0310050] Ba. Bar observed a second new narrow state in the Ds*+ p 0 invariant mass distribution near 2. 46 Ge. V/c 2 La Thuile - 2004 15 sidebands subtraction Alexis Pompili (U. of Bari & I. N. F. N. )

Channel Likelihood Fit To disentangle these 2 possible Ds. J(2458) decay modes & extract signal parameters: unbinned maximum likelihood fit using the channel likelihood method contribution from Ds. J(2458) decays combinatorial background BELLE CLEO observed them in continuum and… Belle both in continuum and in B decays [ 16 ]

SPIN-PARITY Decay to JP=0 - mesons only natural spin-parity allowed [0+, 1 -, 2+, …] JP=0+ suggested by: 1) low mass compared to Ds 1(2535) & Ds. J*(2573) 2) absence of decay to Ds+g (not allowed if JP=0+) 3) absence of decay to Ds+p+p- (not allowed if JP=0+) Un-natural spin-parity more likely (lack of decays to DK) Belle helicity analysis from B-decays favours J=1 Decay to Dsp+p- (by Belle) allowed by JP=1+ EXPERIMENTAL SUMMARY Two narrow states observed, in the inclusive Dsp 0 & Ds*p 0 invariant mass distributions, near 2. 317 Ge. V/c 2 & 2. 458 Ge. V/c 2. The widths [G<10 Me. V] are consistent with experimental resolution. The most likely assignment for their spin-parity is 0+ & 1+. La Thuile - 2004 17 Alexis Pompili (U. of Bari & I. N. F. N. )

Spectroscopy of states (before & after) Potential models of [heavy-quark | light-quark] mesons: so far reasonable success for spectroscopy of D, Ds, B, Bs systems ? ? D*K p DK New states do not fit well : masses below the DK[D*K] threshold. IF interpreted as ordinary states, they decay mainly by isospin-violating p-emission thus having widths quite narrow. A possible decay mechanism is through a virtual h followed by h-p 0 mixing [Cho-Wise, PRD 49]. p g p S-wave NEW STATES P-wave …as predicted by models based on HQET & chiral symmetry [Bardeen et al. , …] if new states are 0+ & 1+ 40(!) papers by theorists: Exotic (4 -quark, molecule, …) VS Ordinary explanations (HQET+chiral symmetry, …) [j=3/2; NARROW by K-emission] Crucial to measure radiative decays & di-pion emission 18

SUMMARY Competitive D 0 mixing results obtained with 2 different experimental methods are consistent with no mixing and no CP. wrong-sign D 0 mixing limits (95% CL, 57 fb-1; CP-allowed): D 0 lifetime ratio (91 fb-1): Wrong-sign D 0 mixing limits from semileptonic decays coming soon Charmed mesons are a rich laboratory for Heavy Quark studies. After the discovery of D*s. J(2317) and the observation of Ds. J(2458)… … further Ds mesons (spectroscopic) studies are ongoing. Ba. Bar is a promising place to study charm physics … studies have just began ! La Thuile - 2004 19 Alexis Pompili (U. of Bari & I. N. F. N. )

Backup Slides

Unbinned maximum likelihood fit S 1 t. D Psig(mi) (1 -f 2)(1 -f 3) SIGNAL S 2 + f 2(1 -f 3) s 3 + f 3 proper-time RESOLUTION t. BKG + f 0(1 -f 4) (1 -f 0) [1 -Psig(mi)] BKG La Thuile - 2004 e flying BKG NO-flying BKG f 0 f 4 BACKUP-1 BUT with. . . SBKG S 1 SBKG S 2 s 3 s 4 fixed for tails A. Pompili (U. of Bari & I. N. F. N. )

Statistical error on lifetime extracted from the fit La Thuile - 2004 BACKUP-2 A. Pompili (U. of Bari & I. N. F. N. )

Fit allowed x’ 2<0. Central values for fits of both separate samples gave x’ 2<0. 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 2 D likelihood distributions. Moreover these ones depend strongly on the most likely fitted values of x’ 2 and y. 95% C. L. limits are determined using toy Monte Carlo samples at each point on the contour (frequentistic approach). (x’ 2, y) points on separate contours are combined in pairs to determine (x’ 2, y) on 95% CP contours. Systematic uncertainties included by calculating equivalent statistical deviation for each systematic check and expanding the 95% C. L. contour appropriately. La Thuile - 2004 BACKUP-3 A. Pompili (U. of Bari & I. N. F. N. )

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

Unbinned maximum likelihood fit Assign likelihood to each event for: – Ds. J(2458)+ Ds*(2112)+ 0 – Ds. J(2458)+ Ds. J*(2317)+ – Combinatorial Ds+ 0 bkgd – Ds*(2112)+ + random 0 – Ds. J*(2317)+ + random – Ds. J(2458)+ Ds*(2112)+ 0 … using wrong The Ds. J(2458) signal for a particular decay mode can be isolated by calculating a weight for each Dsp 0 g combination proportional to the relative likelihood contributed by the decay mode of interest La Thuile - 2004 BACKUP-5 A. Pompili (U. of Bari & I. N. F. N. )