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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2022). Measurement of the c-jet mistagging efficiency in t(t)over-bar events using pp collision data at root s=13 TeV collected with the ATLAS detector. Eur. Phys. J. C, 82(1), 95–27pp.
Abstract: A technique is presented to measure the efficiency with which c-jets are mistagged as b-jets (mistagging efficiency) using t (t) over bar events, where one of theW bosons decays into an electron or muon and a neutrino and the other decays into a quark-antiquark pair. The measurement utilises the relatively large and known W -> cs branching ratio, which allows ameasurement to be made in an inclusive c-jet sample. The data sample used was collected by the ATLAS detector at root s = 13 TeV and corresponds to an integrated luminosity of 139 fb(-1). Events are reconstructed using a kinematic likelihood technique which selects the mapping between jets and t (t) over bar decay products that yields the highest likelihood value. The distribution of the b-tagging discriminant for jets from the hadronic W decays in data is compared with that in simulation to extract the mistagging efficiency as a function of jet transverse momentum. The total uncertainties are in the range 3-17%. The measurements generally agree with those in simulation but there are some differences in the region corresponding to the most stringent b-jet tagging requirement.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., Castillo Gimenez, V., et al. (2022). Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 TeV with the ATLAS detector. Eur. Phys. J. C, 82(2), 105–41pp.
Abstract: This paper presents a measurement of the electroweak production of two jets in association with a Z gamma pair, with the Z boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vectorboson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at root s = 13 TeV collected with the ATLAS detector and corresponding to an integated luminosity of 139 fb(-1). The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak Z gamma production in association with two jets is observed in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31 +/- 0.29 fb. An observed (expected) upper limit of 0.37 (0.34(-0.10)(+0.15)) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson into a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 (0.017(-0.005)(+0.007)), assuming the Standard Model production cross-section for a 125 GeV Higgs boson.
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Rinaldi, M., & Vento, V. (2022). Glueballs at high temperature within the hard-wall holographic model. Eur. Phys. J. C, 82(2), 140–10pp.
Abstract: In this investigation an holographic description of the deconfined phase transition of scalar and tensor glueballs is presented within the so called hard-wall model. The spectra of these bound states of gluons have been calculated from the linearized Einstein equations for a graviton propagating from a thermal AdS(5) space to an AdS Black-Hole. In this framework, the deconfined phase is reached via a two steps mechanism. We propose that the transition between the AdS thermal sector to the BH is described via a first order phase transition, with discontinuous masses at the critical temperature, which has been determined by Herzog's method of regulating the free energy densities. Then, the glueball masses diverge with increasing T in the BH phase and thus lead to deconfined states a la Hagedorn.
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Biryukov, V. M., & Ruiz Vidal, J. (2022). Improved experimental layout for dipole moment measurements at the LHC. Eur. Phys. J. C, 82(2), 149–11pp.
Abstract: The electric and magnetic dipole moment of charm and bottom baryons can be measured for the first time by using bent crystal technology at the LHC. The experimental method, proposed in recent years, suffers from limited statistics, which dominates the uncertainty of the measurement. In this work, we present an alternative experimental layout, based on the use of crystal lenses, that improves the trapping efficiency by about a factor 15 (35) for a 2-cm (5-mm) target with respect to the nominal layout, with plain crystal faces. The efficiencies are evaluated taking into account the constraints from the LHC machine, and the technical challenges to realize this novel experimental method are discussed.
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Baeza-Ballesteros, J., Donini, A., & Nadal-Gisbert, S. (2022). Dynamical measurements of deviations from Newton's 1/r(2) law. Eur. Phys. J. C, 82(2), 154–30pp.
Abstract: In Ref. Donini and Marimon (Eur Phys J C 76:696, arXiv:1609.05654, 2016), an experimental setup aiming at the measurement of deviations from the Newtonian 1/r(2) distance dependence of gravitational interactions was proposed. The theoretical idea behind this setup was to study the trajectories of a “Satellite” with a mass m(S) similar to O(10(-9)) g around a “Planet” with mass m(P) is an element of [10(-7), 10(-5)] g, looking for precession of the orbit. The observation of such feature induced by gravitational interactions would be an unambiguous indication of a gravitational potential with terms different from 1/r and, thus, a powerful tool to detect deviations from Newton's 1/r(2) law. In this paper we optimize the proposed setup in order to achieve maximal sensitivity to look for such Beyond-Newtonian corrections. We then study in detail possible background sources that could induce precession and quantify their impact on the achievable sensitivity. We finally conclude that a dynamical measurement of deviations from newtonianity can test Yukawa-like corrections to the 1/r potential with strength as low as alpha similar to 10(-2) for distances as small as lambda similar to 10 μm.
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