11 research outputs found
On direct observation of millicharged particles at - factories and other -colliders
Hypothetical particles with tiny electric charges (millicharged particles or
MCPs) can be produced in electron-positron annihilation if kinematically
allowed. Typical searches for them at colliders exploit a signature of
a single photon with missing energy carried away by the undetected MCP pair. We
put forward an idea to look alternatively for MCP energy deposits inside a
tracker, which is a direct observation. The new signature is relevant for
non-relativistic MCPs, and we illustrate its power on the example of the
- factory, where we argued that the corresponding searches may be
background-free. We find that it can probe the MCP charge down to
of the electron charge for the MCP masses in MeV
vicinity of each energy beam value where the factory will collect a luminosity
of 100 fb in one year. This mass region is unreachable with the searches
for missing energy and single photon.Comment: 12 pages, 3 figures; v2: the background-free signature is introduce
Proposal of the Muon System for the Super Tau-Charm Factory
The first results of the Super Charm-Tau factory muon system simulation are presented: estimation of the main characteristics such as space resolution and muon identification efficiency. A design of the muon system for the Super Charm-Tau factory based on the organic scintillator + WLS fiber + SiPM is proposed
Exclusive open-charm near-threshold cross sections in a coupled-channel approach
Data on 7 open-charm channels collected by the Belle Collaboration are analyzed simultaneously using a unitary approach based on a coupled channel model in a wide energy range = 3.7 − 4.7 GeV. The resulting fit provides a remarkably good overall description of the line shapes in all studied channels. Parameters of 5 vector charmonium resonances are extracted from the fit. It is demonstrated, that this approach could be used account for all exclusive channels and thus solve the long-term problem of the charmonium spectra near threshold
On direct observation of millicharged particles at c-τ factories and other e+e−-colliders
Hypothetical particles with tiny electric charges (millicharged particles or MCPs) can be produced in electron-positron annihilation if kinematically allowed. Typical searches for them at e+e− colliders exploit a signature of a single photon with missing energy carried away by the undetected MCP pair. We put forward an idea to look alternatively for MCP energy deposits inside a tracker, which is a direct observation. The new signature is relevant for non-relativistic MCPs, and we illustrate its power on the example of the c-τ factory, where we argued that the corresponding searches may be background-free. We find that it can probe the MCP charge down to 3×10−3 of the electron charge for the MCP masses in O(5) MeV vicinity of each energy beam value where the factory will collect a luminosity of 100 fb−1 in one year. This mass region is unreachable with the searches for missing energy and single photon
Measurement of the branching fractions for Cabibbo-suppressed decays and at Belle
International audienceWe present measurements of the branching fractions for the singly Cabibbo-suppressed decays and , and the doubly Cabibbo-suppressed decay , based on 980 of data recorded by the Belle experiment at the KEKB collider. We measure these modes relative to the Cabibbo-favored modes and . Our results for the ratios of branching fractions are , , and , where the uncertainties are statistical and systematic, respectively. The second value corresponds to , where is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for and yields , , and , where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction
Measurement of the production ratio in collisions at the resonance using decays at Belle
We measure the ratio of branching fractions for the decays to and using and samples, where stands for ( or ), with fb of data collected at the resonance with the Belle detector. We find the decay rate ratio of over to be , which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in
Measurement of branching fractions of and at Belle
We present a study of a singly Cabibbo-suppressed decay and a Cabibbo-favored decay based on 980 of data collected by the Belle detector, operating at the KEKB energy-asymmetric collider. We measure their branching fractions relative to : and . Combining with the world average , we have the absolute branching fractions: and . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on . The mode is observed for the first time and has a statistical significance of . The branching fraction of has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon
Measurement of the lifetime at Belle II
We report on a measurement of the lifetime using decays reconstructed in data collected by the Belle II experiment and corresponding to of integrated luminosity. The result, , agrees with recent measurements indicating that the is not the shortest-lived weakly decaying charmed baryon