|
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of the B-c(-) meson production fraction and asymmetry in 7 and 13 TeV pp collisions. Phys. Rev. D, 100(11), 112006–17pp.
Abstract: The production fraction of the B-c(-) meson with respect to the sum of B- and (B) over bar (0) mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy pp collisions produced by the Large Hadron Collider (LHC), using the LHCb detector. The rate, approximately 3.7 per mine, does not change with energy, but shows a transverse momentum dependence. The B-c(-) – B-c(+) production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent.
|
|
|
|
Coppola, M., Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2020). Weak decays of magnetized charged pions in the symmetric gauge. Phys. Rev. D, 101(3), 034003–13pp.
Abstract: We consider the decay pi(-) -> l (nu) over bar (l) (l = e(-) , mu(-)) in the presence of an arbitrary large uniform magnetic field, using the symmetric gauge. The consequences of the axial symmetry of the problem and the issue of angular momentum conservation arc discussed in detail. In particular, we analyze the projection of both the canonical and the mechanical total angular momenta along the direction of the magnetic field. It is found that while the former is conserved in the symmetric gauge, the latter is not conserved in both the symmetric and Landau gauges. We derive an expression for the integrated pi(-) -> l (nu) over bar (l) width that coincides exactly with the one we previously found using the Landau gauge, providing an explicit test of the gauge independence of that result. Such an expression implies that for nonzero magnetic fields the decay width does not vanish in the limit in which the outgoing charged leptons can be considered as massless, i.e., it does not exhibit the helicity suppression found in the case of no external field.
|
|
|
|
Di Valentino, E., Melchiorri, A., Mena, O., & Vagnozzi, S. (2020). Nonminimal dark sector physics and cosmological tensions. Phys. Rev. D, 101(6), 063502–20pp.
Abstract: We explore whether nonstandard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are (a) an interaction between the dark matter and dark energy components and (b) a dark energy equation of state w different from that of the canonical cosmological constant w = -1. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. Moreover, a clear degeneracy exists between these two parameters in the case of cosmic microwave background (CMB) data. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder H-0 measurements of Riess et al. (R19), as well as recent baryon acoustic oscillation (BAO) and type Ia supernovae (SNeIa) distance data. We find that in quintessence coupled dark energy models, where w > -1, the evidence for a nonzero coupling between the two dark sectors can surpass the 5 sigma significance. Moreover, for both Planck + BAO or Planck + SNeIa, we find a preference for w > -1 at about three standard deviations. Quintessence models are, therefore, in excellent agreement with current data when an interaction is considered. On the other hand, in phantom coupled dark energy models, there is no such preference for a nonzero dark sector coupling. All the models we consider significantly raise the value of the Hubble constant, easing the H-0 tension. In the interacting scenario, the disagreement between Planck thorn BAO and R19 is considerably reduced from 4.3 sigma in the case of the Lambda cold dark matter (Lambda CDM) model to about 2.5 sigma. The addition of low-redshift BAO and SNeIa measurements leaves, therefore, some residual tension with R19 but at a level that could be justified by a statistical fluctuation. Bayesian evidence considerations mildly disfavor both the coupled quintessence and phantom models, while mildly favoring a coupled vacuum scenario, even when late-time datasets are considered. We conclude that nonminimal dark energy cosmologies, such as coupled quintessence, phantom, or vacuum models, are still an interesting route toward softening existing cosmological tensions, even when low-redshift datasets and Bayesian evidence considerations are taken into account.
|
|
|
|
T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2019). Measurement of neutrino and antineutrino neutral-current quasielasticlike interactions on oxygen by detecting nuclear deexcitation gamma rays. Phys. Rev. D, 100(12), 112009–19pp.
Abstract: Neutrino- and antineutrino-oxygen neutral-current quasielasticlike interactions are measured at Super-Kamiokande using nuclear deexcitation gamma rays to identify signal-like interactions in data from a 14.94(16.35) x 10(20) protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are <sigma(nu-NCQE)> = 1.70 +/- 0.17(stat.)(-0.38)(+0.51) (syst.) x 10(-38) cm(2)/oxygen with a flux-averaged energy of 0.82 GeV and <sigma((nu) over bar -NCQE)> = 0.98 +/- 0.16(stat.)(-0.19)(+0.26)(syst.) x 10(-38)cm(2)/oxygen with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed.
|
|
|
|
Miralles, V., & Pich, A. (2019). LHC bounds on colored scalars. Phys. Rev. D, 100(11), 115042–11pp.
Abstract: We analyze the constraints on colored scalar bosons imposed by the current LHC data at root s = 13 TeV. Specifically, we consider an additional electroweak doublet of color-octet scalars, satisfying the principle of minimal flavor violation in order to fulfill the stringent experimental limits on flavor-changing neutral currents. We demonstrate that colored scalars with masses below 800 GeV are already excluded, provided they are not fermiophobic.
|
|
