ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2019). Search for squarks and gluinos in final states with hadronically decaying tau-leptons, jets, and missing transverse momentum using pp collisions at root s=13 TeV with the ATLAS detector. Phys. Rev. D, 99(1), 012009–34pp.
Abstract: A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau-lepton is presented. Two exclusive final states with either exactly one or at least two tau-leptons are considered. The analysis is based on proton-proton collisions at root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1) delivered by the Large Hadron Collider and recorded by the ATLAS detector in 2015 and 2016. No significant excess is observed over the Standard Model expectation. At 95% confidence level, model-independent upper limits on the cross section are set and exclusion limits are provided for two signal scenarios: a simplified model of gluino pair production with tau-rich cascade decays, and a model with gauge-mediated supersymmetry breaking (GMSB). In the simplified model, gluino masses up to 2000 GeV are excluded for low values of the mass of the lightest supersymmetric particle (LSP), while LSP masses up to 1000 GeV are excluded for gluino masses around 1400 GeV. In the GMSB model, values of the supersymmetry-breaking scale are excluded below 110 TeV for all values of tan beta in the range 2 <= tan beta <= 60, and below 120 TeV for tan beta > 30.
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Debastiani, V. R., & Navarra, F. S. (2019). A non-relativistic model for the [cc][(c)over-bar(c)over-bar] tetraquark. Chin. Phys. C, 43(1), 013105–20pp.
Abstract: We use a non-relativistic model to study the spectroscopy of a tetraquark composed of [cc][(c) over bar(c) over bar] in a diquark-antidiquark configuration. By numerically solving the Schrodinger equation with a Cornell-inspired potential, we separate the four-body problem into three two-body problems. Spin-dependent terms (spin-spin, spin-orbit and tensor) are used to describe the splitting structure of the c (c) over bar spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spin-dependent interaction is sizable in the diquark-antidiquark system, despite the heavy diquark mass, and also that the diquark has a finite size if treated in the same way as the c (c) over bar systems. We find that the lowest S-wave T-4c tetraquarks might be below their thresholds of spontaneous dissociation into low-lying charmonium pairs, while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds. Finally, we repeat the calculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks. This might be relevant to the study of exotic charmonium in the quark-gluon plasma. The T4c states could be investigated in the forthcoming experiments at the LHC and Belle II.
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Carames, T. F., Vijande, J., & Valcarce, A. (2019). Exotic bc(q)over-bar(q)over-bar four-quark states. Phys. Rev. D, 99(1), 014006–9pp.
Abstract: We carry out a systematic study of exotic QQ'(q) over bar(q) over bar four-quark states containing distinguishable heavy flavors, b and c. Different generic constituent models are explored in an attempt to extract general conclusions. The results are robust, predicting the same sets of quantum numbers as the best candidates to lodge bound states independently of the model used, the isoscalar J(P) = 0(+) and J(P) = 1(+) states. The first state would be strong and electromagnetic-interaction stable, while the second would decay electromagnetically to (B) over barD gamma. Isovector states are found to be unbound, preventing the existence of charged partners. The interest on exotic heavy-light tetraquarks with nonidentical heavy flavors comes reinforced by the recent estimation of the production rate of the isoscalar bc (u) over bar(d) over bar J(P) = 1(+) state, 2 orders of magnitude larger than that of the bb (u) over bar(d) over bar analogous state.
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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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AGATA Collaboration(Kaya, L. et al), & Gadea, A. (2019). Identification of high-spin proton configurations in Ba-136 and Ba-137. Phys. Rev. C, 99(1), 014301–19pp.
Abstract: The high-spin structures of Ba-136 and Ba-137 are investigated after multinucleon-transfer (MNT) and fusion-evaporation reactions. Ba-136 is populated in a Xe-136 + U-238 MNT reaction employing the high-resolution Advanced GAmma Tracking Array (AGATA) coupled to the magnetic spectrometer PRISMA at the Laboratori Nazionali di Legnaro, Italy, and in two Be-9 + Te-130 fusion-evaporation reactions using the High-efficiency Observatory for gamma-Ray Unique Spectroscopy (HORUS) at the FN tandem accelerator of the University of Cologne, Germany. Furthermore, both isotopes are populated in an elusive reaction channel in the B-11 + Te-130 fusion-evaporation reaction utilizing the HORUS gamma-ray array. The level scheme above the J(pi) = 10(+) isomer in Ba-136 is revised and extended up to an excitation energy of approximately 5.5 MeV. From the results of angular-correlation measurements, the E-x = 3707- and E-x = 4920-keV states are identified as the bandheads of positive- and negative-parity cascades. While the high-spin regimes of both Te-132 and Xe-134 are characterized by high-energy 12(+) -> 10(+) transitions, the Ba-136 E2 ground-state band is interrupted by negative-parity states only a few hundred keV above the J(pi) = 10(+) isomer. Furthermore, spins are established for several hitherto unassigned high-spin states in Ba-137. The new results close a gap along the high-spin structure of N < 82 Ba isotopes. Experimental results are compared to large-scale shell-model calculations employing the GCN50:82, Realistic SM, PQM130, and SN100PN interactions. The calculations suggest that the bandheads of the positive-parity bands in both isotopes are predominantly of proton character.
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Chiang, C. W., Cottin, G., & Eberhardt, O. (2019). Global fits in the Georgi-Machacek model. Phys. Rev. D, 99(1), 015001–21pp.
Abstract: Off the beaten track of scalar singlet and doublet extensions of the Standard Model, triplets combine an interesting LHC phenomenology with an explanation for neutrino masses. The Georgi-Machacek model falls into this category, but it has never been fully explored in a global fit. We use the HEPfit package to combine recent experimental Higgs data with theoretical constraints and obtain strong limits on the mixing angles and mass differences between the heavy new scalars as well as their decay widths. We also find that the current signal strength measurements allow for a Higgs to vector boson coupling with an opposite sign to the Standard Model, but this possibility can be ruled out by the lack of direct evidence for heavy Higgs states. For these hypothetical particles, we identify the dominant decay channels and extract bounds on their branching ratios from the global fit, which can be used to single out the decay patterns relevant for the experimental searches.
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Fileviez Perez, P., Golias, E., Li, R. H., Murgui, C., & Plascencia, A. D. (2019). Anomaly-free dark matter models. Phys. Rev. D, 100(1), 015017–15pp.
Abstract: We investigate the predictions of anomaly-free dark matter models for direct and indirect detection experiments. We focus on gauge theories where the existence of a fermionic dark matter candidate is predicted by anomaly cancellation, its mass is defined by the new symmetry breaking scale, and its stability is guaranteed by a remnant symmetry after the breaking of the gauge symmetry. We find an upper bound on the symmetry breaking scale by applying the relic density and perturbative constraints. The anomaly-free property of the theories allows us to perform a full study of the gamma lines from dark matter annihilation. We investigate the correlation between predictions for final-state radiation processes and gamma lines. Furthermore, we demonstrate that the latter can be distinguished from the continuum gamma-ray spectrum.
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Dombos, A. C., Spyrou, A., Naqvi, F., Quinn, S. J., Liddick, S. N., Algora, A., et al. (2019). beta-decay half-lives of neutron-rich nuclides in the A=100-110 mass region. Phys. Rev. C, 99(1), 015802–8pp.
Abstract: beta-decay half-lives of neutron-rich nuclides in the A = 100-110 mass region have been measured using an implantation station installed inside of the Summing NaI(T1) (SuN) detector at the National Superconducting Cyclotron Laboratory. Accurate half-lives for these nuclides are important for nuclear astrophysics, nuclear structure, and nuclear technology. The half-lives from the present work are compared with previous measurements, showing overall good agreement.
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Dai, L. R., Yu, Q. X., & Oset, E. (2019). Triangle singularity in tau(-) -> nu(tau)pi(-) f(0)(980) (a(0)(980)) decays. Phys. Rev. D, 99(1), 016021–13pp.
Abstract: We study the triangle mechanism for the decay tau(-) -> nu(tau)pi(-) f(0)(980) with the f(0)(980) decaying into pi(+) pi(-). The mechanism for this process is initiated by tau(-) -> nu K-tau*(0) K- followed by the K*(0) decay into pi K--(+), then the K- K+ produce the f(0)(980) through a triangle loop containing K* K+ K- which develops a singularity around 1420 MeV in the pi f(0)(980) invariant mass. We find a narrow peak in the pi(+) pi(-) invariant mass distribution, which originates from the f(0)(980) amplitude. Similarly, we also study the triangle mechanism for the decay tau -> nu pi(-) a(0)(980), with the a(0)(980) decaying into pi(0)eta.The formalism leads to final branching ratios for pi(-) f(0)(980) and pi(-) a(0)(980) of the order of 4 x 10(-4) and 7 x 10(-5), respectively, which are within present measurable range. Experimental verification of these predictions will shed light on the nature of the scalar mesons and on the origin of the “a(1)(1420)” peak observed in other reactions.
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Albiol, F., Corbi, A., & Albiol, A. (2019). Densitometric Radiographic Imaging With Contour Sensors. IEEE Access, 7, 18902–18914.
Abstract: We present the technical/physical foundations of a new imaging technique that combines ordinary radiographic information (generated by conventional X-ray settings) with the patient's volume to derive densitometric images. Traditionally, these images provide quantitative information about tissues densities. In our approach, they graphically enhance either soft or bony regions. After measuring the patient's volume with contour recognition devices, the physical traversed lengths within it (as the Roentgen beam intersects the patient) are calculated and pixel-wise associated with the original radiograph (X). In order to derive this map of lengths (L), the camera equations of the X-ray system and the contour sensor are determined. The patient's surface is also translated to the point-of-view of the X-ray beam and all its entrance/exit points are sought with the help of ray-casting methods. The derived L is applied to X as a physical operation (subtraction), obtaining soft tissue-(D-S) or bone-enhanced (D'(B)) figures. In the D-S type, the contained graphical information can be linearly mapped to the average electronic density (traversed by the X-ray beam). This feature represents an interesting proof-of-concept of associating density data to radiographs, but most important, their intensity histogram is objectively compressed, i.e., the dynamic range is more shrunk (compared against the corresponding X). This leads to other advantages: improvement in the visibility of border/edge areas (high gradient), extended manual window level/width manipulations during screening, and immediate correction of underexposed X instances. In the D-B' type, high-density elements are highlighted and easier to discern. All these results can be achieved with low-energy beam exposures, saving costs and dose. Future work will deepen this clinical side of our research. In contrast with other image-based modifiers, the proposed method is grounded on the measurement of a physical entity: the span of the X-ray beam within a body while undertaking a radiographic examination.
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