共查询到20条相似文献,搜索用时 31 毫秒
1.
E. Govorkova 《Physics of Atomic Nuclei》2016,79(11-12):1474-1476
The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B + → J/ψK *+(→ K +π0) and B + → J/ψK + decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. 相似文献
2.
I. M. Belyaev E. M. Govorkova V. Yu. Egorychev D. V. Savrina 《Moscow University Physics Bulletin》2015,70(6):497-503
The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B + → J/ψK*+(→K +π0) and B + → J/ψK + decays. The efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb–1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. 相似文献
3.
Recent results on B-hadron physics in ATLAS are reviewed. A new measurement of CP-violating parameters in B s → J/ψφ decay is performed on full Run 1 statistics. Branching fraction BR(B s → μ+μ?) = (0.9 ?0.8 +1.1 )×10?9 is measured, below the Standard Model (SM) prediction. 相似文献
4.
Attention is paid to the production mechanisms of light scalars that reveal their nature. We reveal the chiral shielding of the σ(600) meson. We show that the kaon loop mechanism of the ? radiative decays, ratified by experiment, is four-quark transition and points to the four-quark nature of light scalars. We show also that the light scalars are produced in the two photon collisions via four-quark transitions in contrast to the classic P wave tensor qq? mesons that are produced via two-quark transitions γγ → qq?. We study the mechanism of production of the light scalar mesons in the D s + → π+π? e +ν decays: D s + → ss?e +ν → [σ(600) + f 0(980)]e +ν → π+π? e +ν, and compare it with the mechanism of production of the light pseudoscalar mesons in the D s + → (η/η′)e +ν decays: D s + → ss?e +ν → (η/η′)e +ν. As a result we find support to four-quark nature of light scalars. In the end, we outline the future research program. 相似文献
5.
The work is devoted to the study of b-s anomaly decays. We evaluated branching fractions of B → K*μ+μ?, B s 0 → φμ+μ? and Bs→ μ+μ? decays and compared them with available experimental data and with results from other theoretical approaches. 相似文献
6.
N. V. Nikitin S. Yu. Sivoklokov L. N. Smirnova D. A. Tlisov K. S. Toms 《Physics of Atomic Nuclei》2007,70(12):2086-2102
The possibility of recording the rare muonic decays B d,s 0 → μ + μ ? at the ATLAS detector (LHC, CERN) is studied. The question of what results can be expected within the first three years of LHC operation in the initial-luminosity mode is examined. The most important noncombinatorial background processes are listed for rare muonic decays of B mesons. 相似文献
7.
The latest results of searching for exotic multiquark states with heavy quarks obtained in the D0 experiment (Fermi National Accelerator Laboratory, USA) are presented. In particular, the evidence of existence of a possible four-quark state X(5568) → B s 0 π±in the cases with hadronic and semileptonic decay channels of B s 0 meson is considered, as well as the results of searching for the five-quark states in the J/ψΛ system. 相似文献
8.
Fermionic and weak decays of the scalar leptoquarks S = S 1 (+) , S 1 (?) , and S m and the scalar gluons F = F 1 and F 2 predicted by the minimal model involving four-color symmetry and the Higgs mechanism of quark-and lepton-mass splitting are considered. The widths and the branching ratios are calculated for these decays, and the results are analyzed versus the couplings and masses of decaying particles. It is shown that, at relatively small mass splittings Δm within scalar doublets (Δm < m W), the fermionic decays S 1 (+) → tl j + , S 1 (?) → v i \(\tilde b\), S m → t \(\tilde \nu \) j, F 1 → t \(\tilde b\), and F 2 → t \(\tilde t\), which are characterized by few-GeV widths for m S, m F < 1 TeV and decay branching ratios close to unity, are dominant, but that, for Δm > m W, the weak decays S → S′W and F → F’W compete with the above fermionic decays. In the case of m S < m t, the processes S 1 (+) → cl j + , S 1 (?) → v i \(\tilde b\), S m → bl j + , and S m → c \(\tilde \nu \) j, whose total branching ratios are Br(S 1 (+) → cl +) ≈ Br(S 1 (?) → v \(\tilde b\)) ≈ 1, Br(S m → bl +) ≈ 0.9, and Br(S m → c \(\tilde \nu \)) ≈ 0.1, appear to be dominant decays of scalar leptoquarks. Searches for these decays at LHC and the Tevatron are of interest. 相似文献
9.
D. A. Ivanishchev V. G. Ryabov Yu. G. Ryabov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(6):721-726
The unique design of the PHENIX detector at the Relativistic Heavy-Ion Collider allows one to detect neutral and charged particles produced in high-energy collisions of heavy ions. This circumstance made it possible to measure many-particle decays of light mesons, such as K S 0 →π0π0, η→π0π?π+, and η→γγ in p + p, d + Au and Au + Au collisions at the energy \(\sqrt {S_{NN} }\) = 200 GeV. The latest results of measuring the differential production cross sections, ratios of particle yields (K S 0 /π0 and η/π0), and the nuclear modification factors (\(R_{dA}^{K_S }\), R dA η , R AA η ) in a wide range of transverse momenta (from 2 to 12 GeV s?1) are reported. 相似文献
10.
The spectral and power characteristics of radiation of the second positive system of nitrogen (C 3Π u → B 3Π g ) in Ar-N2 and Ar-N2-Cl2 mixtures excited by barrier discharge have been studied experimentally. Addition of argon to N2 increased the radiation power by sixfold. In the triple mixture Ar-N2-Cl2 = 210/0.5/0.005, minor chlorine additions increased the intensity of the C 3Π u → B 3Π g transition by 26% compared to Ar-N2 mixtures. Radiation power density of 2.7 mW/cm2 has been achieved. In both binary and triple mixtures, the second positive system of nitrogen was the major contributor to radiation, while the contributions of the fourth positive system of N 2 * (D 3Σ u + → B 3Π g ), the Vegard-Kaplan transition of N 2 * (A 3Σ u + → X 1Σ g + ), and the D′ → A′ band of Cl 2 * were negligibly small. 相似文献
11.
The branching ratios and differential distributions for the four-leptonic decays \({B^ - } \to {\mu ^ + }{\mu ^ - }{\bar v_e}{e^ - }\), \({B^ - } \to {e^ + }{e^ - }{\bar v_\mu }{\mu ^ - }\), and \({B^ - } \to {\mu ^ + }{\bar v_\mu }{\mu ^ - }{\mu ^ - }\) are calculated within the Standard Model. The branching ratios for the rare decays Bd,s → e+e?μ+μ? and Bd,s → μ+μ?μ+μ? are estimated. Methods for testing the lepton universality in rare multileptonic decays of charged and neutral B mesons are proposed. 相似文献
12.
O. Fedin 《Physics of Particles and Nuclei》2017,48(5):760-762
This paper presents the complete set of polarization angular coefficients A 0?7 describing lepton angular distributions in Z boson decay, which were measured at the ATLAS experiment in proton–proton collisions with the energy √s = 8 TeV. Theoretical values for the difference A 0 ? A 2 calculated in the fixed-order QCD perturbation theory O(α s 2 ), demonstrate significant deviation from the measured data, which indicates the necessity of taking into account higher order corrections. The evidence of nonzero coefficients A 5,6,7 was obtained for the first time, in accordance with theoretical calculations in O(α s 2 ) approximation. Measurement of the polarization angular coefficients A i is important for subsequent precision measurement of parameters of the electroweak model at the LHC, such as the sine of Weinberg electroweak mixing angle sin2 θ W and the W boson mass. 相似文献
13.
High-frequency broad-band (65–240 GHz) EPR is used to study impurity centers of bivalent chromium in a CdGa2S4 crystal. It is found that the EPR spectra correspond to tetragonal symmetry. The spin Hamiltonian H = βB · g · S + B 2 0 O 2 0 + B 4 0 O 4 0 + B 4 4 O 4 4 with the parameters B 2 0 =23659±2 MHz, B 4 0 =1.9±1 MHz, |B 4 4 |=54.2±2 MHz, g‖=1.93±0.02, and g⊥=1.99±0.02 is used to describe the observed spectra. It is concluded that chromium ions occupy one of the tetrahedrally coordinated cation positions. 相似文献
14.
S. M. Polikarpov I. M. Belyaev V. J. Egorychev D. V. Savrina 《Physics of Atomic Nuclei》2016,79(2):288-291
The first ever observation of the decay process B0 → J/ψη′ is described. The branching ratios were measured for the decay processes B(s) → J/ψη(′), and the η–η′ mixing angles were determined on this basis. The first indication of the occurrence of the decay process Bs → ψ(2S)η′ is presented. The respective analysis was performed on the basis of data accumulated with the LHCb detector in proton–proton collisions at the c.m. collision energies of 7 and 8 TeV and the integrated luminosity of 3 fb?1. 相似文献
15.
Precise measurements on rare radiative B decays are performed with the LHCb experiment at LHC. The LHCb results regarding the ratio of branching fractions for two radiative decays, B 0 → K *0 γ and B s → ?γ, the direct CP asymmetry in B 0 → K *0 γ decay channel and the observation of the photon polarization in the B ± → K ±π?π± γ decay, are included. The first two measurements were performed in 1 fb–1 of pp collisions data and the third one in 3 fb–1 of data, respectively. 相似文献
16.
M. E. Akopyan I. Yu. Novikova S. A. Poretsky A. M. Pravilov A. G. Smolin T. V. Fedorova 《Optics and Spectroscopy》2005,99(1):36-42
The emission spectra caused by the transitions from the ion-pair states and f0 g + and G1g of the I2 molecule are obtained by excitation of individual rovibronic levels of the molecule by the method of optical-optical double resonance. The emission spectra from the state F0 u + populated due to collisions I2(f) + I2(X) are also measured. By modeling the experimental emission spectra, the dipole moment functions for the electronic transitions f g + -B0 u + , A0 u + , and B″0 u + ; G1g-A0 u + and B″0 u + ; and F0 u + -X0 g + and a′0 g + of the iodine molecule are reconstructed. 相似文献
17.
Mixing of K 0 and B 0 mesons is studied in the scope of the minimum supersymmetry model (MSSM) with a type II Yukawa sector and explicit violation of CP invariance in the Higgs potential. The mixing parameters Δm LS and ? are calculated in the limit of the low-energy four-fermion approximation with a charged Higgs boson exchange. It is shown that supersymmetric effects are very small for K 0 mesons and may be quite significant for B s 0 and B d 0 mesons, which imposes constraints on the MSSM parameter space. 相似文献
18.
The magnetostriction of the NiFeCrO4 ferrite is investigated for the first time. It is found that the frustration of magnetic coupling occurs only in the B sublattice of the NiFeCrO4 ferrite, whereas the A sublattice has a usual magnetic structure. The inference is made that the frustration of magnetic coupling in the B sublattice is caused not only by the negative direct BB exchange interaction Cr B 3+ -Cr B 3+ but also by the positive indirect AB exchange interaction Fe A 3+ -O2?-Cr B 3+ . Reasoning from the experimental data and an analysis of the exchange interactions in the NiFeCrO4 ferrite sample, it is demonstrated for the first time that the magnetic moments of Fe A 3+ ions in this ferrite deviate from collinearity. It is established that, at low temperatures, the B sublattice of the NiFeCrO4 ferrite is responsible for the total magnetic moment n0exp. 相似文献
19.
E. A. Gastilovich V. G. Klimenko N. V. Korol’kova R. N. Nurmukhametov S. A. Serov 《Optics and Spectroscopy》2005,99(1):28-35
The strengths (P 00 s )2 and F VSO 2 of the transitions from the triplet sublevels s = z, y, and x of the electronic state 3A″ of the phenyldibenzophosphole (DB(P-Ph)) molecule are calculated taking into account the intramolecular spin-orbit (SO) and joint vibronic-spin-orbit (VSO) interactions. The contributions to the vibronic transition strengths from the SO interactions in different structural elements of the molecule (the C atoms of the dibenzene framework, the P atom, and the Ph substituent) are determined. The effect of the nonplanar nuclear configuration of the DB(P-Ph) molecule on the values of F VSO s is investigated. The radiative deactivation rate constants of the k rad s triplet sublevels T s are estimated. It is found that the vibrations of the A′(B1) symmetry in the fine-structure phosphorescence spectrum of DB(P-Ph) occur due to both the SO coupling exclusively in the P atom and the T x → S0 transition (the x axis is perpendicular to the planar dibenzene framework of the molecule) with a high (preferential) population of this triplet sublevel. 相似文献
20.
The first 2+ states in N=20 isotones are studied within the self-consistent quasiparticle random phase approximation based on the Green’s function method. The residual interaction between quasiparticles with full velocity dependence is consistently derived from the Skyrme interaction plus pairing interaction energy density functional. The B(E2, 0 1 + → 2 1 + ) transition probabilities and the excitation energies of the first 2+ states are well described within a single framework. We discuss mainly the microscopic origin of the anomalously large B(E2) value and the very low excitation energy in 32Mg. 相似文献