Search for four-quark and six-quark exotic states with charm and strange quarks

• Applicant: Dr. Elisabetta Prencipe
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389090153

We plan the study of narrow, possibly exotic hadronic states in e+e- continuum with the combined, complete BaBar and Belle data sets. This would represent the first combined Belle and BaBar analysis in spectroscopy. The X(4140), and higher similar states discovered recently, of supposedly 4-quark content [c cbar s sbar] have been observed in B meson decays, yet the presently the experimental evidence is controversial. We propose to investigate for the first time the e+e- continuum, which is not available at experiments with hadron collisions.The DsJ(2317) is one of the prime exotic candidate states, as its mass is observed about 160 MeV lower than quark model predictions, which otherwise are very accurate to describe masses of many other charm-strange mesons Our proposal includes:(1) the search for a signal of the X(4140) and similar states in the [DsDs*] invariant mass systems. If a signal is observed, this would represent a second decay channel, and thus establish the states as resonances and exclude the intrepretation as kinematic effects(e.g. thresholds).Without the combination of the BaBar and Belle data sets, this analysis would suffer of insufficient statistics due to low reconstruction efficiency of neutral pions in the DsJ decay.The [J/Psi phi] invariant mass system will be analyzed as well, trying to establish the X(4140) as reference signal.In a second step, the search for even more exotic, yet unobserved states in the[DsDsJ(2317)] invariant mass system. Assuming possibly a 4-quark nature ofthe DsJ(2317), a signal would be a candidate for a 6-quark state.(2) Measurement of the total width of the DsJ(2317) in the sub-MeV regime. We plan to employ multi-dimensional fits with kinematical overconstraints to reach the required sensitivity, which has been already demonstrated by Belle to be possible for the widths of the Ds(2536) and the X(3872). For this purpose, we will use the decay Bs -> DsDs(2317)pi0. In Bs decays, production of [s sbar] is enhanced compared to B decays.This precision analysis requires kinematical variables of the initial state, which are only available in B(s) decays and not in the continuum. The reconstruction efficiency of pi0 detection is a factor ~100-1000 higher than at LHCb.

• DFG Programme: Research Grants