Search results for "Boson"

Search for a light Higgs resonance in radiative decays of theϒ(1S)with a charm tag

2015

A search is presented for the decay Υ(1S)→ γA^0, A^0 → cc[bar], where A^0 is a candidate for the CP-odd Higgs boson of the next-to-minimal supersymmetric standard model. The search is based on data collected with the BABAR detector at the Υ(2S) resonance. A sample of Υ(1S) mesons is selected via the decay Υ(2S)→π + π − Υ(1S). The A^0 → cc[bar] decay is identified through the reconstruction of hadronic D^0, D^+, and D^∗ (2010)^+ meson decays. No significant signal is observed. The measured 90% confidence-level upper limits on the product branching fraction B(Υ(1S) → γA^0 ) × B(A^0 → cc[bar] ) range from 7.4×10^(−5) to 2.4×10^(−3) for A^0 masses from 4.00 to 8.95  GeV/c^2 and 9.10 to 9.25  Ge…

Invisible width of the Z-boson and “secret” ν-ν interactions

1993

Abstract The width of the decay Z→ν ν ν ν in the presence of a possible nonstandard four-fermion ν-ν interaction is calculated. From the invisible width of the Z-boson measured at LEP the upper bound on the strength F of such an effective interaction has been obtained: F≲4×102GF. This bound is about three orders of magnitude lower than earlier existing particle physics bounds and it is comparable with an estimate that can be obtained from supernova neutrino data. The expression for the spectrum of leptons in the decays W→lν l ν ν is also presented.

Electromagnetic production of polarization in hypernuclei.

1991

The formation of polarized hypernuclei through kaon photoproduction is investigated in a distorted-wave impulse approximation approach. The polarization depends strongly on the model used to describe the elementary process. For one particular model and certain well populated states the amount of polarization may reach up to 50%. We present cross sections and polarizations for kaon photoproducton on $^{16}\mathrm{O}$, $^{28}\mathrm{Si}$, $^{56}\mathrm{Fe}$, and $^{89}\mathrm{Y}$ and demonstrate the sensitivity of polarization to distortion and nonlocal effects. More information on the elementary process is needed before the feasibility of such measurements can be established.

Meson and isobar degrees of freedom in light nuclei

1983

The role of mesonic and isobar degrees of freedom in various electromagnetic processes is reviewed for light nuclei. Special emphasis is laid on the deuteron, which allows the cleanest answers within the non-relativistic framework. The origin of the photonuclear enhancement with respect to both exchange forces and exchange currents is discussed in detail.

10.7 Weak quark mixing and the CKM matrix

2008

Proton emission off nuclei induced by kaons in flight

2010

We study the (K-, p) reaction on nuclei with a 1 GeV/c momentum kaon beam, paying special attention to the region of emitted protons having kinetic energy above 600 MeV, which was used to claim a deeply attractive kaon nucleus optical potential. Our model describes the nuclear reaction in the framework of a local density approach and the calculations are performed following two different procedures: one is based on a many-body method using the Lindhard function and the other is based on a Monte Carlo simulation. The simulation method offers flexibility to account for processes other than kaon quasielastic scattering, such as K- absorption by one and two nucleons, producing hyperons, and all…

Quasimolecular resonances in terms of dipole and quadrupole interacting bosons

1986

The energy spectrum of the /sup 12/C+ /sup 12/C resonances is described with the interacting boson (quadrupole) model. The Hamiltonians corresponding to the three dynamical symmetries and to the general case of the model are used. The results are compared with the similar calculations within the nuclear vibron (dipole) model. Based on the present experimental data no choice can be made between the dipole and quadrupole descriptions, but in both cases the best fit is quite close to the dynamical symmetry corresponding to a soft vibrator.

Measurement of Z 0 -boson production at large rapidities in Pb–Pb collisions at

2018

The production of Z0 bosons at large rapidities in Pb–Pb collisions at √sNN=5.02TeV is reported. Z0 candidates are reconstructed in the dimuon decay channel (Z0→μ+μ−), based on muons selected with pseudo-rapidity −4.0 20GeV/c. The invariant yield and the nuclear modification factor, RAA, are presented as a function of rapidity and collision centrality. The value of RAA for the 0–20% central Pb–Pb collisions is 0.67±0.11(stat.)±0.03(syst.)±0.06(corr. syst.), exhibiting a deviation of 2.6σ from unity. The results are well-described by calculations that include nuclear modifications of the parton distribution functions, while the predictions using vacuum PDFs deviate from data by 2.3σ in the 0…

Shape dynamics in neutron-rich Kr isotopes: Coulomb excitation of 92Kr, 94Kr and 96Kr

2013

We report on the study of excited states in 92,94,96Kr populated via projectile Coulomb excitation at safe energies. The radioactive ion beams at energies of 2.85 MeV/u were delivered by the REX-ISOLDE facility at CERN and impinged on self-supporting 194,196Pt targets. The emitted γ -rays were detected by the Miniball detector-array. A detailed description of the experimental techniques used for extracting diagonal and transitional matrix elements and of the theoretical framework is given. The present experiment reveals the moderate evolution of the collective structure in the considered neutron-rich Kr isotopic chain, which is supported by the interacting boson model combined with the self…

Inclusive charged-current neutrino-nucleus reactions

2011

We present a model for weak CC induced nuclear reactions at energies of interest for current and future neutrino oscillation experiments. This model is a natural extension of the work of Refs.[1,2], where the QE contribution to the inclusive electron and neutrino scattering on nuclei was analyzed. The model is based on a systematic many body expansion of the gauge boson absorption modes that includes one, two and even three body mechanisms, as well as the excitation of Delta isobars. The whole scheme has no free parameters, besides those previously adjusted to the weak pion production off the nucleon cross sections in the deuteron, since all nuclear effects were set up in previous studies o…