|
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Search for A ' -> mu(+)mu(-) Decays. Phys. Rev. Lett., 124(4), 041801–12pp.
Abstract: Searches are performed for both promptlike and long-lived dark photons, A ', produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A '->mu(+)mu(-) decays using a data sample corresponding to an integrated luminosity of 5.5 fb(-1) collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the gamma-A ' kinetic mixing strength. The promptlike A ' search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214 < m(A ') less than or similar to 740 MeV and 10.6 < m(A ') less than or similar to 30 GeV. The search for long-lived A '->mu(+)mu(-) decays places world-leading constraints on low-mass dark photons with lifetimes O(1)ps.
|
|
|
|
El-Neaj, Y. A. et al, & Bernabeu, J. (2020). AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space. EPJ Quantum Technol., 7(1), 6–27pp.
Abstract: We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. KCL-PH-TH/2019-65, CERN-TH-2019-126
|
|
|
|
Ikeno, N., Ono, A., Nara, Y., & Ohnishi, A. (2020). Effects of Pauli blocking on pion production in central collisions of neutron-rich nuclei. Phys. Rev. C, 101(3), 034607–9pp.
Abstract: Pauli blocking is carefully investigated for the processes of NN <-> N Delta and Delta -> N pi in heavy-ion collisions, aiming at a more precise prediction of the pi(-)/pi(+) ratio which is an important observable to constrain the high-density symmetry energy. We use the AMD + JAM approach, which combines the antisymmetrized molecular dynamics for the time evolution of nucleons and the Jet AA Microscopic transport model to treat processes for Delta resonances and pions. As is known in general transport-code simulations, it is difficult to treat Pauli blocking very precisely due to unphysical fluctuations and additional smearing of the phase-space distribution function, when Pauli blocking is treated in the standard method of JAM. We propose an improved method in AMD + JAM to use the Wigner function precisely calculated in AMD as the blocking probability. Different Pauli blocking methods are compared in heavy-ion collisions of neutron-rich nuclei, Sn-132+Sn-124, at 270 MeV/nucleon. With the more accurate method, we find that Pauli blocking is stronger, in particular for the neutron in the final state in NN -> N Delta and Delta -> N pi, compared to the case with a proton in the final state. Consequently, the pi(-)/pi(+) ratio becomes higher when the Pauli blocking is improved, the effect of which is found to be comparable to the sensitivity to the high-density symmetry energy.
|
|
|
|
Bayar, M., Ikeno, N., & Oset, E. (2020). Analysis of the psi (4040) and psi (4160) decay into D-(*()) (D)over-bar(()*()), D-s(()*()) (D)over-bar(s)(()*()). Eur. Phys. J. C, 80(3), 222–9pp.
Abstract: We have performed an analysis of the e+e--> D(*) data in the region of the psi(4040) and psi(4160) resonances which have a substantial overlap and require special care. By using the P-3(0) model to relate the different D(*)(D) over bar(*) production modes, we make predictions for production of these channels and compare with experiment and other theoretical approaches. As a side effect we find that these resonances qualify largely as c (c) over bar states and theweight of the meson-meson components in the wave function is very small.
|
|
|
|
Husek, T., & Leupold, S. (2020). Radiative corrections for the decay Sigma(0) -> Lambda e(+)e(-). Eur. Phys. J. C, 80(3), 218–24pp.
Abstract: Electromagnetic form factors serve to explore the intrinsic structure of nucleons and their strangeness partners. With electron scattering at low energies the electromagnetic moments and radii of nucleons can be deduced. The corresponding experiments for hyperons are limited because of the unstable nature of the hyperons. Only for one process this turns to an advantage: the decay of the neutral Sigma hyperon to a Lambda hyperon and a real or virtual photon. Due to limited phase space the effects caused by the Sigma-to-Lambda transition form factors compete with the QED radiative corrections for the decay sigma 0 -> e+e-. These QED corrections are addressed in the present work, evaluated beyond the soft-photon approximation, i.e., over the whole range of the Dalitz plot and with no restrictions on the energy of the radiative photon.
|
|
