Results 1 - 10 of 40994
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[en] In the doubly magic nucleus Pb states at excitation energies 6 ≲ E< 7.0 MeV populated by the inelastic proton scattering via the doublet isobaric analog resonances g+d in Bi are studied. Sixteen states containing dominant strengths of the configurations gp, dp, gf, df are newly assigned spins from 2 to 6, among them ten states are newly identified. Amplitudes with relative signs of up to four one-particle one-hole configurations with strengths down to 0.05% are determined in 40 states with spins from 1 to 6. Amplitudes of configurations dp, dp, df for fourteen states and amplitudes of gp, gp, gf for twenty-seven states are determined. Total strengths up to the full strength are found for configurations dp, dp, df with spins from 1 to 3 and for gp, gp, gf with spins from 1 to 6.
[en] The β decay endpoint energies corresponding to the decay from Pm to levels in Sm have been measured for the first time. The measurement has been made with a β - γ coincidence setup of two thin window Planar HPGe detectors and four Clover HPGe detectors. This measurement is a part of the program, taken up at VECC, on β - γ spectroscopy that would be utilized to characterise long lived β decaying isomers in nuclei.
[en] The cross-section for the lowest order 2→2 elastic scattering between two charged scalars under external magnetic field mediated via a neutral scalar, has been computed in strong as well as weak magnetic field limits. This has been done by applying the optical theorem where the cross-section is expressed in terms of the imaginary parts of different one-loop graphs contributing to the forward scattering amplitudes. The modification in the amplitudes due to the external magnetic field has been done by means of replacing the charged scalar propagators with the Schwinger proper-time ones. Significant modifications of the cross-sections with respect to the vacuum cross-section are observed due to the external magnetic field.
[en] It has been observed in the literature that measurements of low-mass Drell–Yan (DY) transverse momentum spectra at low center-of-mass energies are not well described by perturbative QCD calculations in collinear factorization in the region where transverse momenta are comparable with the DY mass. We examine this issue from the standpoint of the Parton Branching (PB) method, combining next-to-leading-order (NLO) calculations of the hard process with the evolution of transverse momentum dependent (TMD) parton distributions. We compare our predictions with experimental measurements at low DY mass, and find very good agreement. In addition we use the low mass DY measurements at low to determine the width q of the intrinsic Gauss distribution of the PB-TMDs at low evolution scales. We find values close to what has earlier been used in applications of PB-TMDs to high-energy processes at the Large Hadron Collider (LHC) and HERA. We find that at low DY mass and low even in the region of p/m ∼ 1 the contribution of multiple soft gluon emissions (included in the PB-TMDs) is essential to describe the measurements, while at larger masses (m ∼ m) and LHC energies the contribution from soft gluons in the region of p/m ∼ 1 is small.
[en] Time delay of the photons coupled to the Weyl tensor in a regular phantom black hole is investigated in both weak and strong deflection gravitational lensing. We find that the time delay in the weak deflection lensing strongly depends on the phantom hair while the delay in the strong deflection lensing is significantly affected by the hair and the strength of the coupling. We suggest that it is necessary to measure these two kind of time signals for fully understanding and distinguishing such an interaction beyond the standard Einstein–Maxwell theory.
[en] We consider models with any number of Higgs doublets and study the conditions for decoupling. We show that, under very general circumstances, all the quadratic coefficients of the scalar potential must be present, except in special cases, which include terms related to directions of vanishing vacuum expectation values. We give a few examples. Moreover, we show that the decoupling of all charged scalars implies the decoupling of all extra neutral scalars and vanishing CP violation in scalar-pseudoscalar mixing.
[en] The purpose of this paper is to get second-order gravitational equations, a correction made to Jefimenko’s linear gravitational equations. These linear equations were first proposed by Oliver Heaviside in , making an analogy between the laws of electromagnetism and gravitation. To achieve our goal, we will use perturbation methods on Einstein field equations. It should be emphasized that the resulting system of equations can also be derived from Logunov’s non-linear gravitational equations, but with different physical interpretation, for while in the former gravitation is considered as a deformation of space-time as we can see in [2,3,4,5], in the latter gravitation is considered as a physical tensor field in the Minkowski space-time (as in [6,7,8]). In Jefimenko’s theory of gravitation, exposed in [9, 10], there are two kinds of gravitational fields, the ordinary gravitational field, due to the presence of masses, at rest, or in motion and other field called Heaviside field due to and acts only on moving masses. The Heaviside field is known in general relativity as Lense-Thirring effect or gravitomagnetism (The Heaviside field is the gravitational analogous of the magnetic field in the electromagnetic theory, its existence was proved employing the Gravity Probe B launched by NASA (See, for example, [11, 12]). It is a type of gravitational induction), interpreted as a distortion of space-time due to the motion of mass distributions, (see, for example [13, 14]). Here, we will present our second-order Jefimenko equations for gravitation and its solutions.
[en] In the framework of holography, we discuss on the phase transition behavior from a novel Gauss–Bonnet AdS black hole discovered in [Phys. Rev. Lett. 124, 081301 (2020)] in both charged and neutral cases. First, we explore the thermodynamic behavior for the black hole entropy by investigating T−S diagram, specific heat capacity and free energy, and we find that, in the T−S plane, the black hole exhibits a van der Waals phase transition similar to that in P−V plane in extended phase space. Secondly, we detect thermodynamic phase transition for the two point correlation function, and find that, the van der Waals phase transition can also be displayed in the T−δL plane which is completely similar to that of black hole entropy in the T−S plane. Our result turns out that, not only the charged but also neutral cases, we can observe holographic van der Waals phase transition for the novel Gauss–Bonnet AdS black hole by employing the black hole entropy and two point correlation function.
[en] A recent analysis from the PHENIX collaboration of available direct photon measurement results in collisions of various systems such as Au+Au, Cu+Cu, and Pb+Pb, at different beam energies ranging from 39 to 2760 GeV, has shown a universal, within experimental uncertainties, multiplicity scaling, in which direct photon p-spectra for transverse momenta up to 2 GeV/c are scaled with charged hadron pseudorapidity density at midrapidity raised to power α=1.25. On the other hand, those direct photon p-spectra also exhibit geometrical scaling in the similar p range. Assuming power-law dependence of the scaled photon spectra for both scaling laws, we formulate two independent conditions for the power α, which overshoot experimental data by ∼10% on average. We discuss possible sources that might improve this estimate.
[en] In this paper we study cosmological solutions of the f(T, B) gravity using dynamical system analyses. For this purpose, we consider cosmological viable functions of f(T, B) that are capable of reproducing the dynamics of the Universe. We present three specific models of f(T, B) gravity which have a general form of their respective solutions by writing the equations of motion as an autonomous system. Finally, we study its hyperbolic critical points and general trajectories in the phase space of the resulting dynamical variables which turn out to be compatible with the current late-time observations.