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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., et al. (2017). Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV pp collisions. J. High Energy Phys., 12(12), 034–52pp.
Abstract: A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of b-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at root s = 13 TeV, which corresponds to 36.1 fb(-1) of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered.
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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. (2017). Measurement of the B-+/- production cross-section in pp collisions at root s=7 and 13 TeV. J. High Energy Phys., 12(12), 026–25pp.
Abstract: The production of B +/- mesons is studied in pp collisions at centre-of-mass energies of 7 and 13 TeV, using B-+/- -> J/psi K-+/- decays and data samples corresponding to 1.0 fb(-1) and 0.3 fb(-1), respectively. The production cross-sections summed over both charges and integrated over the transverse momentum range 0 < pT < 40 GeV/c and the rapidity range 2.0 < y < 4.5 are measured to be sigma-(pp -> B-+/- X, root s = 7 TeV) = 43.0 +/- 0.2 +/- 2.5 +/- 1.7 μb, sigma(pp -> B-+/- X, root s = 13 TeV) = 86.6 +/- 0.5 +/- 5.4 +/- 3.4 μb, where the first uncertainties are statistical, the second are systematic, and the third are due to the limited knowledge of the B-+/- -> J/psi K-+/- branching fraction. The ratio of the cross-section at 13 TeV to that at 7 TeV is determined to be 2.02 +/- 0.02 (stat) +/- 0.12 (syst). Differential cross-sections are also reported as functions of pi, and y. All results are in agreement with theoretical calculations based on the state-of-art fixed next-to-leading order quantum chromodynamics.
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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. (2017). Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at root s=7 TeV. J. High Energy Phys., 12(12), 025–22pp.
Abstract: Bose-Einstein correlations of same-sign charged pions, produced in proton-proton collisions at a 7TeV centre-of-mass energy, are studied using a data sample collected by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the form of an enhancement of pairs of like-sign charged pions with small four-momentum difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source is investigated, determining both the correlation radius and the chaoticity parameter. The measured correlation radius is found to increase as a function of increasing charged-particle multiplicity, while the chaoticity parameter is seen to decrease.
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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. (2017). Measurement of the Y(nS) polarizations in pp collisions at root s=7 and 8 TeV. J. High Energy Phys., 12(12), 110–60pp.
Abstract: The polarization of the (sic) (1S), (sic) (2S) and (sic) (3S) mesons, produced in pp collisions at centre-of-mass energies root s = 7 and 8TeV, is measured using data samples collected by the LHCb experiment, corresponding to integrated luminosities of 1 and 2 fb(-1), respectively. The measurements are performed in three polarization frames, using (sic) -> μμdecays in the kinematic region of the transverse momentum p(T)((sic)) < 30 GeV/c and rapidity 2.2 < y((sic)) < 4.5. No large polarization is observed.
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Barenboim, G., & Park, W. I. (2017). Lepton number asymmetries and the lower bound on the reheating temperature. J. Cosmol. Astropart. Phys., 12(12), 037–13pp.
Abstract: We show that the reheating temperature of a matter-domination era in the early universe can be pushed down to the neutrino decoupling temperature at around 2 MeV if the reheating takes place through non-hadronic decays of the dominant matter and neutrino-antineutrino asymmetries are still large enough, vertical bar L vertical bar greater than or similar to O(10(-2)) (depending on the neutrino flavor) at the end of reheating.
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