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Ferreiro, A., & Navarro-Salas, J. (2019). Running couplings from adiabatic regularization. Phys. Lett. B, 792, 81–85.
Abstract: We extend the adiabatic regularization method by introducing an arbitrary mass scale μin the construction of the subtraction terms. This allows us to obtain, in a very robust way, the running of the coupling constants by demanding mu-invariance of the effective semiclassical (Maxwell-Einstein) equations. In particular, we get the running of the electric charge of perturbative quantum electrodynamics. Furthermore, the method brings about a renormalization of the cosmological constant and the Newtonian gravitational constant. The running obtained for these dimensionful coupling constants has new relevant (non-logarithmic) contributions, not predicted by dimensional regularization.
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Watanabe, H. et al, & Montaner-Piza, A. (2019). New isomers in (125)Pd(79)( )and Pd-127(81): Competing proton and neutron excitations in neutron-rich palladium nuclides towards the N=82 shell closure. Phys. Lett. B, 792, 263–268.
Abstract: The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N = 82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in Pd-125(79) and Pd-127(81) studied using the EURICA gamma-ray spectrometer, following production via in-flight fission of a high-intensity U-238 beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2(+)) and (19/2(+)) in Pd-125 and Pd-127, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus Sn-132.
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Xie, J. J., & Oset, E. (2019). Search for the Sigma* state in Lambda(+)(c) -> pi(+)pi(0)pi(-)Sigma(+) decay by triangle singularity. Phys. Lett. B, 792, 450–453.
Abstract: A Sigma* resonance with spin-parity J(P) = 1/2(-) and mass in the vicinity of the (K) over barN threshold has been predicted in the unitary chiral approach and inferred from the analysis of CLAS data on the gamma p -> K+pi(0)Sigma(0) reaction. In this work, based on the dominant Cabibbo favored weak decay mechanism, we perform a study of Lambda(+)(c) -> pi(+)pi(0)Sigma* with the possible Sigma* state decaying into pi(-)Sigma(+) through a triangle diagram. This process is initiated by Lambda(+)(c) -> pi(+)(K) over bar *N, then the (K) over bar* decays into (K) over bar pi and (K) over barN produce the Sigma* through a triangle loop containing (K) over bar *N (K) over bar which develops a triangle singularity. We show that the pi(-)Sigma(+) state is generated from final state interaction of (K) over barN in S-wave and isospin I = 1, and the Lambda(+)(c) -> pi(+)pi(0)pi(-)Sigma(+) decay can be used to study the possible Sigma* state around the (K) over barN threshold. The proposed decay mechanism can provide valuable information on the nature of the Sigma* resonance and can in principle be tested by facilities such as LHCb, BelleII and BESIII.
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Chen, P., Ding, G. J., Srivastava, R., & Valle, J. W. F. (2019). Predicting neutrino oscillations with “bi-large” lepton mixing matrices. Phys. Lett. B, 792, 461–464.
Abstract: We propose two schemes for the lepton mixing matrix U = (U1U nu)-U-dagger, where U = U-1 refers to the charged sector, and U-v denotes the neutrino diagonalization matrix. We assume U-nu to be CP conserving and its three angles to be connected with the Cabibbo angle in a simple manner. CP violation arises solely from the U-1, assumed to have the CKM form, U-1 similar or equal to V-CKM, suggested by unification. Oscillation parameters depend on a single parameter, leading to narrow ranges for the “solar” and “accelerator” angles theta(12) and theta(23), as well as for the CP phase, predicted as delta(CP) similar to +/- 1.3 pi.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Measurements of inclusive and differential fiducial cross-sections of t(t)over-bar gamma production in leptonic final states at root s=13 TeV in ATLAS. Eur. Phys. J. C, 79(5), 382–41pp.
Abstract: Inclusive and differential cross-sections for the production of a top-quark pair in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 36.1fb-1, collected by the ATLAS detector at the LHC in 2015 and 2016 at a centre-of-mass energy of 13TeV. The measurements are performed in single-lepton and dilepton final states in a fiducial volume. Events with exactly one photon, one or two leptons, a channel-dependent minimum number of jets, and at least one b-jet are selected. Neural network algorithms are used to separate the signal from the backgrounds. The fiducial cross-sections are measured to be 521 +/- 9(stat.)+/- 41(sys.)fb and 69 +/- 3(stat.)+/- 4(sys.) fb for the single-lepton and dilepton channels, respectively. The differential cross-sections are measured as a function of photon transverse momentum, photon absolute pseudorapidity, and angular distance between the photon and its closest lepton in both channels, as well as azimuthal opening angle and absolute pseudorapidity difference between the two leptons in the dilepton channel. All measurements are in agreement with the theoretical predictions.
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