2011 QCD and High Energy Interactions - Rencontres de Moriond ...

CHARM SPECTROSCOPY AT B FACTORIES
RICCARDO CENCI
(on the behalf of the BABAR and BELLE collaborations)
4315 Department of Physics (Bldg 82), University of Maryland,
College Park, MD 20742-4111, U.S.A.
We report on the most recent measurements of charm spectroscopy obtained using the BABAR
and BELLE datasets.
1 Introduction
The spectrum of quark-antiquark systems was initially predicted in 1985 using a relativistic
chromodynamic potential model 1 and those predictions were updated in 2001 using recent lattice
results 2 . While predictions for lower states are in agreement with the most recent experimental
observations, some discrepanciencies are still present for higher ones.
Charm meson studies can be performed at the B factories experiments, like BABAR and
BELLE, because their datasets include approximately the same number of bb and cc events, being
the cross sections of the two processes comparable at their center-of-mass (CM) energy. Charm
mesons can be selected using two methods: as products of B decays, when the B candidate is
fully reconstruct (exclusive mode), or directly in cc events, where bb events are rejected requiring
a momentum larger than 2.6 GeV/c for the meson candidates (inclusive mode).
In this proceeding, we will describe the most recent charm spectroscopy results obtained by
the BABAR and BELLE experiments 3 .
2 Inclusive study of D + π − , D 0 π + and D ∗+ π − systems using BABAR dataset
In this analysis we study D + π− , D0π + and D∗+ π− final states with the inclusive mode using
a dataset of 454 fb −1 collected by the BABAR detector 4 . To extract the resonance parameters
we define the variable M(D + π− ) = m(K−π + π + π− ) − m(K−π + π + ) + m + D and M(D0π + ) =
m(K−π + π− ) − m(K−π + ) + mD0, where m + D and m0D are the nominal values of the D+ and
D0 mass 5 . We remove the contribution due to fake D + and D0 candidates by subtracting the
M(Dπ) distribution obtained by selecting events in the D + and D0 candidate mass sidebands.
The M(D + π− ) and M(D0π + ) distributions are presented, respectively, in Figs. 1(a) and 1(b).
The two distributions show similar features: prominent peaks for D ∗ 2
(2460), peaking back-
grounds at about 2.3 GeV/c 2 , and new structures around 2.6 and 2.75 GeV/c 2 . The peaking
backgrounds are due to decays from the D1(2420) and D ∗ 2 (2460) where a slow π0 is missing
in the reconstruction. The two distributions are fit to a smooth combinatoric background plus
the appropriate relativistic Breit-Wigner (BW) function for each resonance. Due to broad resonances,
some of their parameters need to be constrained to be around the nominal values 5
or fixed to the values obtained in the D ∗+ π − analysis described below. Because the peaking