physics meeting (ITEP, October 22, 2008)
A short description of the PANDA project at FAIR including a physics program, experimental setup and a Russian institution involvement will be presented.
Experimental data on new charmonia and charmonium-like states are reviewed.
|A.B.Kaidalov (ITEP)|| INTERACTION
OF ANTIPROTONS WITH NUCLEI
Some problems for interactions of antiprotons with nuclei in the energy region of PANDA experiment are considered. It is emphasized that the space-time picture of interaction of hadrons with nuclei changes in this energy region. It is shown that measurements of atomic dependence for cross section of annihilation of antiprotons on nuclei can provide an information on this phenomenon. Other problems: production of hidden and open charm on nuclei, bound charmonia, supernuclei, production of heavy strange baryons and cumulative particles in antiproton-nucleus collisions will be discussed.
Lowest charmonium hybrids are considered in the framework of the QCD string model. All parameters of the model are fixed from the fit for the spectrum of conventional charmonia. Then masses, spin splittings, and relative decay rates into various S- and P-wave D-meson pairs are calculated for charmonium hybrids with a magnetic gluon. Results are compared with the lattice predictions and with the existing experimental data. A possible interpretation of the Y(4260) as a hybrid meson is discussed and consequences of such an identification are outlined.
An effective quark-pion Lagrangian is derived from QCD within the FieldCorrelator method which contains two parameters and decribes variety of processes:from decaysof heavy quarkonia into pair of heavy-light mesons with or without pions (kaons, etas) to transitions between quarkonia states with emission of any number ofpseudoscalars.Comparison with numerous experimental data shows a reasonable agreement and sensitivity to the exact form of quarkonia wave functions. In conclusion a project of future work for all charmonia states with channel coupling and pion interaction within the outlined method is formulated.
The masses of the ground-state and excited heavy tetraquarks with hidden charm and bottom are calculated within the relativistic diquark-antidiquark picture. It is argued that recently observed charmonium-like states X(3872), Y(4260), Y(4360), Z(4248), Z(4433) and Y(4660) could be the tetraquark states with hidden charm.
|M.G.Sapozhnikov (JINR)|| Study
of annihilation reactions with phi-meson
production at PANDA energies
Strong OZI-rule violation on a factor of 30-70 was found in some reactions of the antiproton-annihilation at rest in different experiments at LEAR(CERN). These facts were explained in the framework of different models, including the assumption that the nucleon intrinsic strangeness is polarized. The program of measurements at PANDA for testing prediction of polarized strangeness model for the annihilation in flight is proposed.
FOR THE RADIAL EXCITED STATES OF CHARMONIUM IN EXPERIMENTS USING
ANTIPROTON BEAMS WITH MOMENTUM RANGING FROM 1 GeV/c TO 15 GeV/c.
|A.M.Badalian (ITEP)|| THE
S-D MIXING AND
WIDTHS OF HIGHER CHARMONIUM 1--
The di-electron widths of the conventional Ψ(4040), Ψ(4160), Ψ(4415) resonances are shown to be in good agreement with experiment, if the S-D mixing with a large mixing angle θ=34o takes place. It supposes that the physical resonance Y(~ 4400), which originates from the 3 3D1 state, has also rather large Γee(Y(~4400))=0.061 keV. For the Belle resonance Y(4660) considered as a pure 5 3S1 state Γee(Y(4660))=0.70 keV, but the width becomes significantly smaller, equal 0.31 keV, if the mixing angle between the 5 3S1 and 4 3D1 states has the characteristic value θ=34o. For the 6 3S1 resonance the mass M(6S) =4830 (20) MeV and Γee=0.20 keV are predicted.
SHIFTS AND TRANSITIONS IN HEAVY-LIGHT MESONS
The mass shifts of the P-wave Ds and Bs mesons due to coupling to DK, D*K and BK, B*K channels are studied using the effective chiral quark-pion Lagrangian. The strong mass shifts down ~140 MeV and ~ 100MeV for D*s(0+) and Ds(1+') ~100 MeV for B*s(0+) and Bs(1+') are calculated. The chiral flip mechanism due to the bispinor structure of both heavy-light mesons is very essential. The masses M(B*s(0+)) =5710(15) MeV and M(Bs(1+'))=5730(15) MeV are predicted. Experimental limit on the width Γ(Ds1(2536))<2.3 MeV puts strong restrictions on admittable mixing angle between the 1+ and 1+' states, |φ|<6o.
EFFECTIVE LUMINOSITY FOR PANDA EXPERIMENT
One of the most important goals of FAIR project is caring out an experiment with internal target PANDA. The only way to achieve design luminosity value is to use a pellet target. However, such a target is coming up with short-scale luminosity variation. Peak to mean luminosity ratio can reach a big value unacceptable for detector.
The BETACOOL simulations for typical PANDA parameters show that the effective luminosity in the case of high-luminosity mode can be in two times less than average one if peak to mean luminosity ratio can reach a big value unacceptable for the detector. This effect can limit the count rate of registered events. Some ideas how to avoid this problem are presented.
|N.B. Skachkov (JINR)||
We consider the mechanism of direct photons production for the anti-proton beam energy E_beam = 14 GeV basing on two partonic subprocesses q + qbar -> gamma + gluon and gluon + q -> gamma + q. The contribution of each subprocess depends on the shape of the corresponding partonic distribution. The Monte – Carlo simulation shows a good possibility of signal separation from the background what allows to expect an extraction of the information about gluon and quark distributions in the kinematical region available for PANDA experiment.
PAIR PRODUCTION AT INTERMEDIATE ENERGIES AND THE MAIN BACKGROUNDS
The process of lepton pair production in antiproton-proton collisions at PANDA experiment is simulated for studying the distributions of energy, transverse momentum and angle variables of individual leptons created in a antiquark-quark annihilation subprocess q qbar -> l+ l-. The correlations between mentioned above physical variables and the corresponding distributions of the number of events versus the values of these variables are presented. problems due to the presence of fake leptons that appear from meson decays are discussed also. The main attention is paid to the contributions from the background processes that may contain leptons and to the ways of their discrimination.