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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., et al. (2018). Search for new phenomena using the invariant mass distribution of same-flavour opposite-sign dilepton pairs in events with missing transverse momentum in root s=13 TeV pp collisions with the ATLAS detector. Eur. Phys. J. C, 78(8), 625–38pp.
Abstract: A search for new phenomena in final states containing an e(+)e(-) or m(+)m(-) pair, jets, and large missing transverse momentum is presented. This analysis makes use of proton-proton collision data with an integrated luminosity of 36.1 fb(-1), collected during 2015 and 2016 at a centre of-mass energy Os = 13 TeV with the ATLAS detector at the Large Hadron Collider. The search targets the pair production of supersymmetric coloured particles (squarks or gluinos) and their decays into final states containing an e(+)e(-) or m(+)m(-) pair and the lightest neutralino ((c) over tilde (0)(1)) via one of two next-to-lightest neutralino ((c) over tilde (0)(2)) decay mechanisms: (c) over tilde (0)(2) Z (c) over tilde (0)(1), where the Z boson decays leptonically leading to a peak in the dilepton invariant mass distribution around the Z boson mass; and (c) over tilde (0)(2) l(+)1(-) (c) over tilde (0)(1) with no intermediate l(+)l(-) resonance, yielding a kinematic endpoint in the dilepton invariant mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted using simplified models, and exclude gluinos and squarks with masses as large as 1.85 and 1.3 TeV at 95% confidence level, respectively.
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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. (2018). Measurement of D-s(+/-) production asymmetry in pp collisions at root s=7 and 8 TeV. J. High Energy Phys., 08(8), 008–21pp.
Abstract: The inclusive D-s(+/-) production asymmetry is measured in pp collisions collected by the LHCb experiment at centre-of-mass energies of root s = 7 and 8 TeV. Promptly produced D-s(+/-) mesons are used, which decay as D-s(+/-) -> phi pi(+/-), with phi -> K+ K-. The measurement is performed in bins of transverse momentum, pT, and rapidity, y, covering the range 2.5 < pT < 25 : 0 GeV/c and 2.0 < y < 4.5. No kinematic dependence is observed. Evidence of nonzero D-s(+/-) production asymmetry is found with a significance of 3.3 standard deviations.
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Ceccopieri, F. A., Courtoy, A., Noguera, S., & Scopetta, S. (2018). Pion nucleus Drell-Yan process and parton transverse momentum in the pion. Eur. Phys. J. C, 78(8), 644–12pp.
Abstract: We present a thorough analysis of unpolarized Drell-Yan (DY) pair production in pion-nucleus scattering. On the nucleus side, we use nuclear parton distributions along with parametrisations of the nucleon partonic transverse distribution available in the literature. Partonic longitudinal and transverse distributions of the pion are those obtained in a recent calculation in a Nambu-Jona Lasinio (NJL) framework, with Pauli-Villars regularization. The scale of the NJL model is determined with a minimisation procedure comparing NLO predictions based on NJL evolved pion distributions to rapidity differential DY cross sections data. The resulting distributions are then used to describe, up to next-to-leading logarithmic accuracy, the transverse momentum spectrum of dilepton pairs up to a transverse momentum of 2 GeV. With no additional parameters, fair agreement is found with available pion-nucleus data, confirming the virtues of the NJL description of pion parton structure. We find sizable evolution effects on the shape of the distributions and on the generated average transverse momentum of the dilepton pair. We furthermore discuss the possibility of gaining information about the behavior of the pion unpolarized transverse momentum dependent parton distribution from pion nucleus DY data.
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Alves, J. M., Botella, F. J., Branco, G. C., Cornet-Gomez, F., Nebot, M., & Silva, J. P. (2018). Symmetry constrained two Higgs doublet models. Eur. Phys. J. C, 78(8), 630–17pp.
Abstract: We study two-Higgs-doublet models (2HDM) where Abelian symmetries have been introduced, leading to a drastic reduction in the number of free parameters in the 2HDM. Our analysis is inspired in BGL models, where, as the result of a symmetry of the Lagrangian, there are tree-level scalar mediated Flavour-Changing-Neutral-Currents, with the flavour structure depending only on the CKM matrix. A systematic analysis is done on the various possible schemes, which are classified in different classes, depending on the way the extra symmetries constrain the matrices of couplings defining the flavour structure of the scalar mediated neutral currents. All the resulting flavour textures of the Yukawa couplings are stable under renormalisation since they result from symmetries imposed at the Lagrangian level. We also present a brief phenomenological analysis of the most salient features of each class of symmetry constrained 2HDM.
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Thakore, T., Devi, M. M., Agarwalla, S. K., & Dighe, A. (2018). Active-sterile neutrino oscillations at INO-ICAL over a wide mass-squared range. J. High Energy Phys., 08(8), 022–34pp.
Abstract: We perform a detailed analysis for the prospects of detecting active-sterile oscillations involving a light sterile neutrino, over a large Delta m(41)(2 )range of 10(-5) eV(2) to 10(2) eV(2), using 10 years of atmospheric neutrino data expected from the proposed 50 kt magnetized ICAL detector at the INO. This detector can observe the atmospheric nu(mu), and (nu) over bar (mu) separately over a wide range of energies and baselines, making it sensitive to the magnitude and sign of Arni i over a large range. If there is no light sterile neutrino, ICAL can place competitive upper limit on vertical bar U-mu 4 vertical bar(2) less than or similar to 0.02 at 90% C.L. for Delta m(41)(2) in the range (0.5-5) x 10(-3) eV(2). For the same vertical bar Delta m(41)(2)vertical bar range, ICAL would be able to determine its sign, exploiting the Earth's matter effect in mu(-) and mu(+) events separately if there is indeed a light sterile neutrino in Nature. This would help identify the neutrino mass ordering in the four-neutrino mixing scenario.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo, F. L., et al. (2018). Search for pair production of heavy vector-like quarks decaying into high-(PT) W bosons and top quarks in the lepton-plus-jets final state in pp collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 08(8), 048–41pp.
Abstract: A search is presented for the pair production of heavy vector-like B quarks, primarily targeting B quark decays into a W boson and a top quark. The search is based on 36.1 fb(-1) of pp collisions at root s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, and multiple jets, of which at least one is b-tagged. No significant deviation from the Standard Model expectation is observed. The 95% confidence level lower limit on the B mass is 1350 GeV assuming a 100% branching ratio to Wt. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. The 100% branching ratio limits are found to be also applicable to heavy vector-like X production, with charge +5/3, that decay into Wt. This search is also sensitive to a heavy vector-like B quark decaying into other final states (Zb and Hb) and thus mass limits on B production are set as a function of the decay branching ratios.
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ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Coleiro, A., Colomer, M., Hernandez-Rey, J. J., Illuminati, G., et al. (2018). Long-term monitoring of the ANTARES optical module efficiencies using K-40 decays in sea water. Eur. Phys. J. C, 78(8), 669–8pp.
Abstract: Cherenkov light induced by radioactive decay products is one of the major sources of background light for deep-sea neutrino telescopes such as ANTARES. These decays are at the same time a powerful calibration source. Using data collected by the ANTARES neutrino telescope from mid 2008 to 2017, the time evolution of the photon detection efficiency of optical modules is studied. A modest loss of only 20% in 9 years is observed. The relative time calibration between adjacent modules is derived as well.
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Escudero, M., Witte, S. J., & Rius, N. (2018). The dispirited case of gauged U(1)(B-L) dark matter. J. High Energy Phys., 08(8), 190–30pp.
Abstract: We explore the constraints and phenomenology of possibly the simplest scenario that could account at the same time for the active neutrino masses and the dark matter in the Universe within a gauged U(1)(B-L) symmetry, namely right-handed neutrino dark matter. We find that null searches from lepton and hadron colliders require dark matter with a mass below 900 GeV to annihilate through a resonance. Additionally, the very strong constraints from high-energy dilepton searches fully exclude the model for 150 GeV < m(z') < 3 TeV. We further explore the phenomenology in the high mass region (i.e. masses greater than or similar to O(1) TeV) and highlight theoretical arguments, related to the appearance of a Landau pole or an instability of the scalar potential, disfavoring large portions of this parameter space. Collectively, these considerations illustrate that a minimal extension of the Standard Model via a local U(1)(B-L) symmetry with a viable thermal dark matter candidate is difficult to achieve without fine-tuning. We conclude by discussing possible extensions of the model that relieve tension with collider constraints by reducing the gauge coupling required to produce the correct relic abundance.
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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. (2018). Observation of the decay Lambda(0)(b) -> psi(2S)p pi(-). J. High Energy Phys., 08(8), 131–18pp.
Abstract: The Cabibbo-suppressed decay Lambda(0)(b) -> psi(2S)p pi(-) is observed for the fi rst time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb(-1) of integrated luminosity at centre-of-mass energies of 7, 8 and 13TeV, respectively. The psi(2S) mesons are reconstructed in the mu(+)mu(-) fi nal state. The branching fraction with respect to that of the Lambda(0)(b) -> psi(2S)pK(-) decay mode is measured to be B (Lambda(0)(b) -> psi(2S)p pi(-))/B (Lambda(0)(b) -> psi(2S)pK(-)) = (11.44 +/- 1.3 +/- 0.2)%, where the fi rst uncertainty is statistical and the second is systematic. The psi(2S) p and psi(2S)pi(-) mass spectra are investigated and no evidence for exotic resonances is found.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., Castillo Gimenez, V., et al. (2018). Search for Low-Mass Dijet Resonances Using Trigger-Level Jets with the ATLAS Detector in pp Collisions at root s=13 TeV. Phys. Rev. Lett., 121(8), 081801–20pp.
Abstract: Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450-1800 GeV. The analyzed data set has an integrated luminosity of up to 29.3 fb(-1) and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.
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