Missing Mass Reconstruction of Ds*(2317)± in pp →Ds±Ds(2317)± Vishwajeet Jha PANDA Meeting : GSI March 09

Motivation : To determine the width of the Ds*(2317) Present measurements put upper limit ( Γ < 4.6 MeV) Method: Experiment : Energy scan around the p pbar →DsDs*(2317) threshold , Shape of excitation function gives the width Simulation : At energy above threshold determine the events in signal region and from cross section dependence vs. energy determine the excitation function shape. Present Work : Missing mass reconstruction of Ds*(2317) for one selected energy above threshold

Signal and Background : Inclusive reconstruction of signal ppbar →Ds Ds*(2317) via decay mode Ds→φ π± , φ→K+ K- Signal generated at 4.291 GeV ( 0.1 MeV width for Ds*(2317) state)‏ In addition, several background channels were simulated, Background channels with important contribution in signal region are ppbar →Ds Ds π+ π- , ppbar →Ds Ds 2πo , ppbar →Ds Ds* π0

Signal ( Φ and Ds candidates): σ ~ 4 MeV σ ~ 12 MeV

Missing Mass: Mass window: φ candidates <10 MeV , Ds candidates < 30 MeV σ ~ 6 MeV σ ~ 15 MeV ppbar →Ds Ds*(2317) (Signal)‏ ‏ ppbar →Ds Ds π+ π- (Background)‏

Correlation between reconstructed MDs and Missing mass : ppbar →Ds Ds π+ π- (Background)‏ ppbar →Ds Ds*(2317) (Signal)‏ ‏

MSUM = MDs + MMISS σ ~ 1 MeV

Msum‏ ( w/o Ds mass cut)‏ Reconstruction using LHETRACK: σ ~ 2.5 MeV σ ~ 1.8 MeV Msum‏ ( w/o Ds mass cut)‏ ‏

Vertex Fitting : Vertex cuts have not been employed in analysis so far The vertex fitter (with TPC tracks)‏ has an efficiency of ~25% for the reconstructed Ds candidates from the ppbar → Ds Ds*(2317) ‏ ppbar →Λ Λbar, Λ →pπ- , L=8.72 cm (PDG value =7.89cm)‏

Summary: Simulation studies for ppbar →Ds Ds*(2317) (Signal) have been performed Missing mass reconstruction give σ ~ 1 MeV. Simulation for the excitation function shape near threshold is in progress.