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). Search for heavy charged long-lived particles in the ATLAS detector in 36.1 fb(-1) of proton-proton collision data at root s=13 Te V. Phys. Rev. D, 99(9), 092007–34pp.
Abstract: A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb(-1) of protonproton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks (R-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived R-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop R-hadrons, as well as staus and charginos of 2000, 1250, 1340, 430, and 1090 GeV, respectively.
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Fontoura, C. E., Krein, G., Valcarce, A., & Vijande, J. (2019). Production of exotic tetraquarks QQ(q)over-bar (q)over-bar in heavy-ion collisions at the LHC. Phys. Rev. D, 99(9), 094037–8pp.
Abstract: We investigate the production of exotic tetraquarks, QQ (q) over bar (q) over bar T-QQ (Q = c or b and q = u or d), in relativistic heavy-ion collisions using the quark coalescence model. The T-QQ yield is given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced tetraquark. The tetraquark wave function is obtained from exact solutions of the four-body problem using realistic constituent models. The production yields are typically one order of magnitude smaller than previous estimations based on simplified wave functions for the tetraquarks. We also evaluate the consequences of the partial restoration of chiral symmetry at the hadronization temperature on the coalescence probability. Such effects, in addition to increasing the stability of the tetraquarks, lead to an enhancement of the production yields, pointing towards an excellent discovery potential in forthcoming experiments. We discuss further consequences of our findings for the search of exotic tetraquarks in central Pb + Pb collisions at the LHC.
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Helo, J. C., Hirsch, M., & Ota, T. (2019). Proton decay at one loop. Phys. Rev. D, 99(9), 095021–14pp.
Abstract: Proton decay is usually discussed in the context of grand unified theories. However, as is well known, in the standard model effective theory proton decay appears in the form of higher-dimensional non-renormalizable operators. Here, we study systematically the one-loop decomposition of the d = 6 B + L violating operators. We exhaustively list the possible one-loop ultraviolet completions of these operators and discuss that, in general, two distinct classes of models appear. Models in the first class need an additional symmetry in order to avoid tree-level proton decay. These models necessarily contain a neutral particle, which could act as a dark matter candidate. For models in the second class the loop contribution dominates automatically over the tree-level proton decay, without the need for additional symmetries. We also discuss possible phenomenology of two example models, one from each class, and their possible connections to neutrino masses, LHC searches and dark matter.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). Measurement of the relative B- -> D-0 / D*(0) / D**(0)mu(-)(nu)over-bar(mu) branching fractions using B- mesons from (B)over-bar(S)(2)*(0) decays. Phys. Rev. D, 99(9), 092009–16pp.
Abstract: The decay of the narrow resonance (B) over bar (s2)*(0 )-> B(-)K(+)can be used to determine the B- momentum in partially reconstructed decays without any assumptions on the decay products of the r meson. This technique is employed for the first time to distinguish contributions from D-0, D*(0), and higher-mass charmed states (D(0)) in semileptonic B- decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb(-1) collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV. The resulting branching fractions relative to the inclusive B- -> (DX)-X-0 mu(-)(nu) over bar (mu )are f(D)(0)= B(B- -> D-0 mu(-)(nu) over bar mu/B(B- ->(DX)-D- -X-0 mu(-)(nu) over bar (mu))( )= 0.25( )+/- 0.06, f( D)(0 )= B(B- -> (D(0) -> (DX)-X-0)mu(-)(nu) over bar (mu))/B(B--> (DX)-X-0 mu(-)(nu) over bar (mu)) = 0.21 +/- 0.07, with f(D)*(0) = 1 – f(D)(0) – f(D)(0) making up the remainder.
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Cottin, G., Helo, J. C., Hirsch, M., & Silva, D. (2019). Revisiting the LHC reach in the displaced region of the minimal left-right symmetric model. Phys. Rev. D, 99(11), 115013–4pp.
Abstract: We revisit discovery prospects for a long-lived sterile neutrino N at the LHC in the context of left-right symmetric theories. We focus on a displaced vertex search strategy sensitive to O(GeV) neutrino masses produced via a right-handed W-R boson. Both on-shell and off-shell Drell-Yan production of W-R are considered. We estimate the reach as a function of m(N) and m(WR). With root s = 13 TeV and 300/fb of integrated luminosity, the LHC can probe neutrino masses as high as approximately 30 GeV and m(wR) around 6 TeV. The reach goes up to 11.5 TeV with 3000/tb and m(N) similar to 45 GeV. This represents an improvement of a factor of 2 in sensitivity with respect to earlier work.
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Masud, M., Roy, S., & Mehta, P. (2019). Correlations and degeneracies among the NSI parameters with tunable beams at DUNE. Phys. Rev. D, 99(11), 115032–19pp.
Abstract: The Deep Underground Neutrino Experiment (DUNE) is a leading experiment in neutrino physics which is presently under construction. DUNE aims to measure the yet unknown parameters in the three flavor oscillation scenario which includes discovery of leptonic CP violation, determination of the mass hierarchy and determination of the octant of theta(23). Additionally, the ancillary goals of DUNE include probing the subdominant effects induced by new physics. A widely studied new physics scenario is that of nonstandard neutrino interactions (NSI) in propagation which impacts the oscillations of neutrinos. We consider some of the essential NSI parameters impacting the oscillation signals at DUNE and explore the space of NSI parameters as well as study their correlations among themselves and with the yet unknown CP violating phase, delta appearing in the standard paradigm. The experiment utilizes a wide band beam and provides us with a unique opportunity to utilize different beam tunes at DUNE. We demonstrate that combining information from different beam tunes (low energy and medium energy) available at DUNE impacts the ability to probe some of these parameters and leads to altering the allowed regions in two-dimensional space of parameters considered.
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Carquin, E., Neill, N. A., Helo, J. C., & Hirsch, M. (2019). Exotic colored fermions and lepton number violation at the LHC. Phys. Rev. D, 99(11), 115028–9pp.
Abstract: Majorana neutrino mass models with a scale of lepton number violation of order tem-electron-volts potentially lead to signals at the LHC. Here, we consider an extension of the standard model with a colored octet fermion and a scalar leptoquark. This model generates neutrino masses at two-loop order. We make a detailed Monte Carlo study of the lepton number violating signal at the LHC in this model, including a simulation of standard model backgrounds. Our forecast predicts that the LHC with 300/fb should be able to probe this model up to color-octet fermion masses in the range of (2.6-2.7) TeV, depending on the lepton flavor of the final state.
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Dai, L. Y., Fuentes-Martin, J., & Portoles, J. (2019). Scalar-involved three-point Green functions and their phenomenology. Phys. Rev. D, 99(11), 114015–18pp.
Abstract: We analyze within the framework of resonance chiral theory the < SA(mu)A(nu >) and < SV μV nu > three-point Green functions, where S, A(mu) and V-mu are short for scalar, axial-vector and vector SU(3) hadronic currents. We construct the necessary Lagrangian such that the Green functions fulfill the asymptotic constraints, at large momenta, imposed by QCD at leading order. We study the implications of our results on the spectrum of scalars in the large-N-C limit, and analyze their decays.
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Delhom, A., Macedo, C. F. B., Olmo, G. J., & Crispino, L. C. B. (2019). Absorption by black hole remnants in metric-affine gravity. Phys. Rev. D, 100(2), 024016–12pp.
Abstract: Using numerical methods, we investigate the absorption properties of a family of nonsingular solutions which arise in different metric-affine theories, such as quadratic and Born-Infeld gravity. These solutions continuously interpolate between Schwarzschild black holes and naked solitons with wormhole topology. The resulting spectrum is characterized by a series of quasibound states excitations, associated with the existence of a stable photonsphere.
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Xiao, C. W., Nieves, J., & Oset, E. (2019). Heavy quark spin symmetric molecular states from (D)over-bar(()*())Sigma(()(c)*()) and other coupled channels in the light of the recent LHCb pentaquarks. Phys. Rev. D, 100(1), 014021–6pp.
Abstract: We consider the (D) over bar (()*())Sigma(()(c)*()) states, together with J/psi N and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb Collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as 1/2(-) (D) over bar Sigma(c), 1/2(-) (D) over bar*Sigma(c), and 3/2(-) (D) over bar*Sigma(c), and the isospin I = 1/2. We find another state around 4374 MeV, of the 3/2(-) (D) over bar Sigma(c)* structure, for which indications appear in the experimental spectrum. Two other near degenerate states of a 1/2(-) (D) over bar*Sigma(c)* and 3/2(-) (D) over bar*Sigma(c)* nature are also found around 4520 MeV, which although less clear, are not incompatible with the observed spectrum. In addition, a 5/2(-) (D) over bar*Sigma(c)* state at the same energy appears, which however does not couple to J/psi p in an S wave, and hence, it is not expected to show up in the LHCb experiment.
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