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Caputo, A., Sberna, L., Frias, M., Blas, D., Pani, P., Shao, L. J., et al. (2019). Constraints on millicharged dark matter and axionlike particles from timing of radio waves. Phys. Rev. D, 100(6), 063515–7pp.
Abstract: We derive constraints on millicharged dark matter and axionlike particles using pulsar timing and fast radio burst observations. For dark matter particles of charge epsilon e, the constraint from time of arrival (TOA) of waves is epsilon/m(milli) less than or similar to 10(-8) eV(-1), for masses m(milli) greater than or similar to 10(-6) eV. For axionlike particles, the polarization of the signals from pulsars yields a bound in the axial coupling g/ m(a) less than or similar to 10(-13) Gev(-1)/(10(-22) eV),for m(a) less than or similar to 10(-19) eV. Both bounds scale as (rho/rho(dm))(1/2 )for fractions of the total dark matter energy density rho(dm). We make a precise study of these bounds using TOA from several pulsars, FRB 121102, and polarization measurements of PSR J0437 – 4715. Our results rule out a new region of the parameter space for these dark matter models.
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Coppola, M., Gomez Dumm, D., Noguera, S., & Scoccola, N. N. (2019). Neutral and charged pion properties under strong magnetic fields in the NJL model. Phys. Rev. D, 100(5), 054014–17pp.
Abstract: In the framework of the Nambu-Jona-Lasino (NJL) model, we study the effect of an intense external uniform magnetic field on neutral and charged pion masses and decay form factors. In particular, the treatment of charged pions is carried out on the basis of the Ritus eigenfunction approach to magnetized relativistic systems. Our analysis shows that in the presence of the magnetic field three and four nonvanishing pion-to-vacuum hadronic form factors can be obtained for the case of the neutral and charged pions, respectively. As expected, it is seen that for nonzero magnetic field the pi(0) meson can still be treated as a pseudo Nambu-Goldstone boson, and consequently the corresponding form factors are shown to satisfy various chiral relations. For definite parametrizations of the model, numerical results for pi(0) and pi(+/-) masses and decay constants are obtained and compared with previous calculations given in the literature.
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Anderson, P. R., Clark, R. D., Fabbri, A., & Good, M. R. R. (2019). Late time approach to Hawking radiation: Terms beyond leading order. Phys. Rev. D, 100(6), 061703–5pp.
Abstract: Black hole evaporation is studied using wave packets for the modes. These allow for approximate frequency and time resolution. The leading order late time behavior gives the well-known Hawking radiation that is independent of how the black hole formed. The focus here is on the higher order terms and the rate at which they damp at late times. Some of these terms carry information about how the black hole formed. A general argument is given which shows that the damping is significantly slower (power law) than what might be naively expected from a stationary phase approximation (exponential). This result is verified by numerical calculations in the cases of 2D and 4D black holes that form from the collapse of a null shell.
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Caputo, A., & Reig, M. (2019). Cosmic implications of a low-scale solution to the axion domain wall problem. Phys. Rev. D, 100(6), 063530–10pp.
Abstract: The post-inflationary breaking of Peccei-Quinn (PQ) symmetry can lead to the cosmic domain wall catastrophe. In this paper we show how to avoid domain walls by implementing the instanton interference effect with a new interaction which itself breaks PQ symmetry and confines at an energy scale smaller than Lambda(QCD). We give a general description of the mechanism and consider its cosmological implications and constraints within a minimal model. Contrary to other mechanisms, we do not require an inverse phase transition or fine-tuned bias terms. Incidentally, the mechanism leads to the introduction of new self-interacting dark matter candidates and the possibility of producing gravitational waves in the frequency range of SKA. Unless a fine-tuned hidden sector is introduced, the mechanism predicts a QCD axion in the mass range 1-15 meV.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., et al. (2019). Search for a heavy charged boson in events with a charged lepton and missing transverse momentum from pp collisions at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 100(5), 052013–29pp.
Abstract: A search for a heavy charged-boson resonance decaying into a charged lepton (electron or muon) and a neutrino is reported. A data sample of 139 fb(-1) of proton-proton collisions at root s = 13 TeV collected with the ATLAS detector at the LHC during 2015-2018 is used in the search. The observed transverse mass distribution computed from the lepton and missing transverse momenta is consistent with the distribution expected from the Standard Model, and upper limits on the cross section for pp -> W'-> lv are extracted (l = e or mu). These vary between 1.3 pb and 0.05 tb depending on the resonance mass in the range between 0.15 and 7.0 TeV at 95% confidence level for the electron and muon channels combined. Gauge bosons with a mass below 6.0 and 5.1 TeV are excluded in the electron and muon channels, respectively, in a model with a resonance that has couplings to fermions identical to those of the Standard Model W boson. Cross-section limits are also provided for resonances with several fixed Gamma/m values in the range between 1% and 15%. Model-independent limits are derived in single-bin signal regions defined by a varying minimum transverse mass threshold. The resulting visible cross-section upper limits range between 4.6 (15) ph and 22 (22) ab as the threshold increases from 130 (110) GeV to 5.1 (5.1) TeV in the electron (muon) channel.
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Bruschini, R., & Gonzalez, P. (2019). Radiative decays in bottomonium beyond the long wavelength approximation. Phys. Rev. D, 100(7), 074001–13pp.
Abstract: We revisit the nonrelativistic quark model description of electromagnetic radiative decays in bottomonium. We show that even for the simplest spectroscopic quark model the calculated widths can be in good agreement with data once the experimental masses of bottomonium states and the photon energy are properly implemented in the calculation. For transitions involving the lower lying spectral states this implementation can be easily done via the long wavelength approximation. For transitions where this approximation does not apply we develop a new method of implementing the experimental energy dependencies.
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Yang, W. Q., Mena, O., Pan, S., & Di Valentino, E. (2019). Dark sectors with dynamical coupling. Phys. Rev. D, 100(8), 083509–11pp.
Abstract: Coupled dark matter-dark energy scenarios arc modeled via a dimensionless parameter xi, which controls the strength of their interaction. While this coupling is commonly assumed to be constant, there is no underlying physical law or symmetry that forbids a time-dependent xi parameter. The most general and complete interacting scenarios between the two dark sectors should therefore allow for such a possibility, and it is the main purpose of this study to constrain two possible and well-motivated coupled cosmologies by means of the most recent and accurate early- and late-time universe observations. We find that CMB data alone prefer xi(z) > 0 and therefore a smaller amount of dark matter, alleviating some crucial and well-known cosmological data tensions. An objective assessment of the Bayesian evidence for the coupled models explored here shows no particular preference for the presence of a dynamical dark sector coupling.
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Campanario, F., Czyz, H., Gluza, J., Jelinski, T., Rodrigo, G., Tracz, S., et al. (2019). Standard model radiative corrections in the pion form factor measurements do not explain the a(mu) anomaly. Phys. Rev. D, 100(7), 076004–5pp.
Abstract: In this paper, we address the question of whether the almost four standard deviations difference between theory and experiment for the muon anomalous magnetic moment a(mu) can be explained as a higher-order Standard Model perturbation effect in the pion form factor measurements. This question has, until now, remained open, obscuring the source of discrepancies between the measurements. We calculate the last radiative corrections for the extraction of the pion form factor, which were believed to be potentially substantial enough to explain the data within the Standard Model. We find that the corrections are too small to diminish existing discrepancies in the determination of the pion form factor for different kinematical configurations of low-energy BABAR, BES-III and KLOE experiments. Consequently, they cannot noticeably change the previous predictions for a(mu) and decrease the deviations between theory and direct measurements. To solve the above issues, new data and better understanding of low-energy experimental setups are needed, especially as new direct a(mu) measurements at Fermilab and J-PARC will provide new insights and substantially shrink the experimental error.
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Wang, G. Y., Roca, L., & Oset, E. (2019). Discerning the two K-1 (1270) poles in D-0 -> pi(+) VP decay. Phys. Rev. D, 100(7), 074018–10pp.
Abstract: Within the chiral unitary approach, the axial-vector resonance K-1 (1270) has been predicted to manifest a two-pole nature. The lowest pole has a mass of 1195 MeV and a width of 246 MeV and couples mostly to K*pi, and the highest pole has a mass of 1284 MeV and a width of 146 MeV and couples mostly to rho K. We analyze theoretically how this double-pole structure can show up in D-0 -> pi+VP decays by looking at the vector-pseudoscalar (VP) invariant mass distribution for different VP channels, exploiting the fact that each pole couples differently to different VP pairs. We find that the final (K) over bar*pi and rho(K) over tilde channels are sensible to the different poles of the K-1 (1270) resonance and hence are suitable reactions to analyze experimentally the double-pole nature of this resonance.
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Beltran-Palau, P., Ferreiro, A., Navarro-Salas, J., & Pla, S. (2019). Breaking of adiabatic invariance in the creation of particles by electromagnetic backgrounds. Phys. Rev. D, 100(8), 085014–12pp.
Abstract: Particles are spontaneously created from the vacuum by time-varying gravitational or electromagnetic backgrounds. It has been proven that the particle number operator in an expanding universe is an adiabatic invariant. In this paper we show that, in some special cases, the expected adiabatic invariance of the particle number fails in presence of electromagnetic backgrounds. In order to do this, we consider as a prototype a Sauter-type electric pulse. Furthermore, we also show a close relation between the breaking of the adiabatic invariance and the emergence of the axial anomaly.
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