| Home | [11–20] << 21 22 23 24 25 26 27 28 29 30 >> [31–40] |
|
Di Bari, P., & Hossain Rahat, M. (2024). Split Majoron model confronts the NANOGrav signal and cosmological tensions. Phys. Rev. D, 110(5), 055019–15pp.
Abstract: In the light of the evidence of a gravitational wave background from the NANOGrav 15 yr dataset, we reconsider the split Majoron model as a new physics extension of the standard model able to generate a needed contribution to solve the current tension between the data and the standard interpretation in terms of inspiraling supermassive black hole massive binaries. In the split Majoron model the seesaw right-handed neutrinos acquire Majorana masses from spontaneous symmetry breaking of global U(1)B-L in a strong first order phase transition of a complex scalar field occurring above the electroweak scale. The final vacuum expectation value couples to a second complex scalar field undergoing a low scale phase transition occurring after neutrino decoupling. Such a coupling enhances the strength of this second low scale first order phase transition and can generate a sizeable primordial gravitational wave background contributing to the NANOGrav 15 yr signal. Some amount of extraradiation is generated after neutron-to-proton ration freeze-out but prior to nucleosynthesis. This can be either made compatible with the current upper bound from primordial deuterium measurements or even be used to solve a potential deuterium problem. Moreover, the free streaming length of light neutrinos can be suppressed by their interactions with the resulting Majoron background, and this mildly ameliorates existing cosmological tensions. Thus cosmological observations nicely provide independent motivations for the model.
|
|
Baeza-Ballesteros, J., Copeland, E. J., Figueroa, D. G., & Lizarraga, J. (2024). Gravitational wave emission from a cosmic string loop: Global case. Phys. Rev. D, 110(4), 043522–12pp.
Abstract: We study the simultaneous decay of global string loops into scalar particles (massless and massive modes) and gravitational waves (GWs). Using field-theory simulations in flat space-time of isolated loops with initial length similar to 80-1700 times their core width, we determine the power emitted into scalar particles, P phi , and GWs, P GW , and characterize the loop-decay timescale as a function of its initial length, energy, and angular momentum. We quantify infrared and ultraviolet lattice dependencies of our results. For all type of loops and initial conditions considered, GW emission is always suppressed compared to particles as P GW /P phi approximate to O(10)(v/mp)2 ( 10 )( v/m p ) 2 << 1, where v is the vacuum expectation value associated with string formation. These conclusions are robust for the length-to-width ratios considered, with no indication they should change if the ratio is increased. The results suggest that the GW background from a global string network, such as in dark-matter axion scenarios, will be suppressed compared to previous expectations.
|
|
Montesinos, V., Song, J., Liang, W. H., Oset, E., Nieves, J., & Albaladejo, M. (2024). Study of possible DND* bound states. Phys. Rev. D, 110(5), 054043–11pp.
Abstract: We start from a recently favored picture in which the Ac(2940) and Lambda(c)(2910) correspond mostly to ND* bound states with J(P) = 1=2(-); 3=2(-) respectively, and then add a D as a third particle, looking for the possible binding of the DND* three-body system within the framework of the fixed center approximation. We find that the system is bound with respect to the corresponding Lambda(c)(2940)D, Lambda(c)(2910)D thresholds with a binding of about 60 MeV and a width of about 90 MeV. Alternatively we assume a cluster of ND and a D* meson interacting with the cluster, and we find similar results. The observation of these states of J(P) = 1=2(+); 3=2(+) would provide new and valuable information concerning the DN and D*N interaction, an issue of current debate.
|
|
Garcia-Tecocoatzi, H., Giachino, A., Ramirez-Morales, A., Rivero-Acosta, A., Santopinto, E., & Vaquera-Araujo, C. (2024). Strong decay widths and mass spectra of the 1D, 2P and 2S singly bottom baryons. Phys. Rev. D, 110(11), 114005–52pp.
Abstract: We calculate the 1D, 2P, and 2S mass spectra of the singly bottom baryons and their strong decay widths. The calculations are performed within a harmonic oscillator quark model that incorporates the spin, spin-orbit, isospin, and flavor interactions. To obtain the model parameters, we conducted a fit using only 13 of the 22 experimentally observed states. Our predictions align well with the observed states, showing a root-mean-square deviation of 9.6 MeV. We calculate the three-quark strong decay widths within the P-3(0) model, which has only one free parameter, the pair creation strength gamma(0); this is the first time that the Lambda(b)eta, Sigma(b rho), Sigma(b)*rho, Lambda(b)eta', Lambda(b)omega, Xi K-b, Xi(b)'K, Xi(b)*K, Xi K-b*, Xi(b)'K*, and Xi(b)*K* channels have been considered in the calculation of the strong decay widths of the excited Lambda b states; the Sigma(b)eta, Xi K-b, Sigma(b)rho, Sigma(b)*rho, Lambda(b)rho, Sigma(b)*eta, Sigma(b)eta', Sigma(b)eta', Xi(b)'K , Xi(b)*K , Xi K-b*, Xi(b)'K*, Xi(b)*K*, Sigma(b)omega, Sigma(b)*omega, Sigma B-8(s), Delta B, N(1520)B, N(1535)B, N(1680)B, and N(1720)B channels in the calculation of the strong decay widths of the excited Sigma(b) states; the Lambda K-b*, Xi(b)rho, Xi(b)'rho , Xi(b)*rho, Sigma K-b*, Sigma(b)*K*, Xi(b)eta', Xi(b)eta', Xi(b)*eta', Xi(b)omega , Xi(b)'omega, Xi(b)*omega, Xi(b)phi , Xi(b)'phi, Xi(b)*phi, Xi B-8(s), Sigma B-8*, and Sigma(10) B channels in the calculation of the strong decay widths of the excited Xi(b) and Xi(b)' states; the Xi K-b*, Xi K-b*, Xi(b)*K*, Omega(b)eta, Omega(b)*eta, Omega(b)phi, Omega(b)*phi, Omega(b)eta', Omega b*eta' , Xi B-8, and Xi B-10 channels in the calculation of the strong decay widths of the Omega(b) states. Moreover, in Appendix D, we give the flavor couplings that can be useful for other articles. In Appendix E, our partial decay widths are reported for each open flavor channel; these may be useful to the LHCb, ATLAS, and CMS experimentalists in order to plan in which particular channels to look for missing bottom baryons. The experimental masses and widths of the discovered Lambda(b) (6146)(0) and Lambda(b) (6152)(0) states are consistent with our mass and width predictions for the D-lambda excitations with quantum numbers J(P) = 3/2+ and J(P) = 5/2+, respectively. Moreover, the masses and widths of the new Xi(b) (6327)(0) and Xi(b)(6333)(0) states 2 agree with our calculations for the D-lambda excitations with quantum numbers J(P) = 3/2+ and J(P) = 5/2+, respectively. Finally, we calculate the electromagnetic decay widths from P- wave states to ground states. We give the exact analytical expressions of the spin-flip and orbit-flip transition amplitudes, both of which are functions of the photon-transferred momentum. The electromagnetic decays are dominant when the strong decays are suppressed. A relevant case is the Omega(-)(b) missing spin excitation, with J(P) = 3/2+, which cannot decay strongly, but has a nonvanishing predicted electromagnetic decay width in the Omega(-)(b)gamma channel. Therefore, we suggest the Omega(-)(b)gamma electromagnetic decay channel as a golden channel in which to search for this state. In all of our calculations, we report the uncertainties related to the experimental and model errors by means of the Monte Carlo bootstrap method.
|
|
Barenboim, G., Sanchis, H., Kinney, W. H., & Rios, D. (2024). Bound on thermal y distortion of the cosmic neutrino background. Phys. Rev. D, 110(12), 123535–8pp.
Abstract: We consider the possibility that the cosmic neutrino background might have a nonthermal spectrum, and investigate its effect on cosmological parameters relative to standard A-cold dark matter (ACDM) cosmology. As a specific model, we consider a thermal y- distortion, which alters the distribution function of the neutrino background by depleting the population of low-energy neutrinos and enhancing the highenergy tail. We constrain the thermal y- parameter of the cosmic neutrino background using cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements, and place a 95%-confidence upper bound of y <= 0.043. The y- parameter increases the number of effective relativistic degrees of freedom, reducing the sound horizon radius and increasing the best-fit value for the Hubble constant H 0 . We obtain an upper bound on the Hubble constant of H 0 = 71.12 km/s/Mpc at 95% confidence, substantially reducing the tension between CMB/BAO constraints and direct measurement of the expansion rate from type-Ia supernovae. Including a spectral distortion also allows for a higher value of the spectral index of scalar fluctuations, with a best-fit of n S = 0.9720 +/- 0.0063, and a 95%-confidence upper bound of n S <= 0.9842.
|