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Caballero-Folch, R. et al, Domingo-Pardo, C., Agramunt, J., Algora, A., Rubio, B., & Tain, J. L. (2016). First Measurement of Several beta-Delayed Neutron Emitting Isotopes Beyond N=126. Phys. Rev. Lett., 117(1), 012501–6pp.
Abstract: The beta-delayed neutron emission probabilities of neutron rich Hg and Tl nuclei have been measured together with beta-decay half-lives for 20 isotopes of Au, Hg, Tl, Pb, and Bi in the mass region N greater than or similar to 126. These are the heaviest species where neutron emission has been observed so far. These measurements provide key information to evaluate the performance of nuclear microscopic and phenomenological models in reproducing the high-energy part of the beta-decay strength distribution. This provides important constraints on global theoretical models currently used in r-process nucleosynthesis.
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Jungclaus, A. et al, Gadea, A., & Montaner-Piza, A. (2016). beta decay of semi-magic Cd-130: Revision and extension of the level scheme of In-130. Phys. Rev. C, 94(2), 024303–8pp.
Abstract: The beta decay of the semi-magic nucleus Cd-130 has been studied at the RIBF facility at the RIKEN Nishina Center. The high statistics of the present experiment allowed for a revision of the established level scheme of In-130 and the observation of additional beta feeding to high- lying core-excited states in In-130. The experimental results are compared to shell-model calculations employing a model space consisting of the full major N = 50-82 neutron and Z = 28-50 proton shells and the NA-14 interaction, and good agreement is found.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., Ruiz Valls, P., et al. (2016). Search for Structure in the B-s(0)pi(+/-) Invariant Mass Spectrum. Phys. Rev. Lett., 117(15), 152003–9pp.
Abstract: The B-s(0)pi(+/-) invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb(-1) of pp collision data at root s 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B-s(0)pi(+/-) final state. The same limits also apply to a possible exotic meson decaying through the chain B-s(*0)pi(+/-), B-s(*0) -> B-s(0) gamma where the photon is excluded from the reconstructed decays.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). First observation of the rare B+ -> D+K+pi(-) decay. Phys. Rev. D, 93(5), 051101–11pp.
Abstract: The B+ -> D+K+pi(-) decay is observed in a data sample corresponding to 3.0 fb(-1) of pp collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is 8 sigma and the branching fraction is measured to be B(B+ -> D+K+pi(-)) = (5.31 +/- 0.90 +/- 0.48 +/- 0.35) x 10(-6), where the uncertainties are statistical, systematic and due to the normalization mode B+ -> D-K+pi(+), respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from B+ -> D*(2)(2460)K-0(+) and B+ -> (D+K*)(892)(0) decays. No significant signals are observed and upper limits are set on their branching fractions.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2016). Observation of the B (s) (0) -> J/psi phi phi decay. J. High Energy Phys., 03(3), 040–18pp.
Abstract: The B (s) (0) -> J/psi phi phi decay is observed in pp collision data corresponding to an integrated luminosity of 3 fb(-1) recorded by the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV. This is the first observation of this decay channel, with a statistical significance of 15 standard deviations. The mass of the B (s) (0) meson is measured to be 5367.08 +/- 0.38 +/- 0.15 MeV/c(2). The branching fraction ratio B[B(s)(0) -> J/psi phi phi]/B[B(s)(0) -> J/psi phi] is measured to be 0.0115 +/- 0.0012 (- 0.0009) (+ 0.0005) . In both cases, the first uncertainty is statistical and the second is systematic. No evidence for non-resonant B(s)(0) -> J/psi phi K (+) K (-) or B(s)(0) -> J/psi K (+) K (-) K (+) K (-) decays is found.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., et al. (2016). Search for the electroweak production of supersymmetric particles in root s=8 TeV pp collisions with the ATLAS detector. Phys. Rev. D, 93(5), 052002–50pp.
Abstract: The ATLAS experiment has performed extensive searches for the electroweak production of charginos, neutralinos, and staus. This article summarizes and extends the search for electroweak supersymmetry with new analyses targeting scenarios not covered by previously published searches. New searches use vector-boson fusion production, initial-state radiation jets, and low-momentum lepton final states, as well as multivariate analysis techniques to improve the sensitivity to scenarios with small mass splittings and low-production cross sections. Results are based on 20 fb(-1) of proton-proton collision data at root s = 8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. The new and existing searches are combined and interpreted in terms of 95% confidence-level exclusion limits in simplified models, where a single production process and decay mode is assumed, as well as within phenomenological supersymmetric models.
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ATLAS Collaboration(Aad, G. et al), Alvarez Piqueras, D., Cabrera Urban, S., Castillo Gimenez, V., Cerda Alberich, L., Costa, M. J., et al. (2016). Combination of searches for WW, WZ, and ZZ resonances in pp collisions at root s=8 TeV with the ATLAS detector. Phys. Lett. B, 755, 285–305.
Abstract: The ATLAS experiment at the CERN Large Hadron Collider has performed searches for new, heavy bosons decaying to WW, WZ and ZZ final states in multiple decay channels using 20.3 fb(-1) of pp collision data at root s = 8 TeV. In the current study, the results of these searches are combined to provide a more stringent test of models predicting heavy resonances with couplings to vector bosons. Direct searches for a charged diboson resonance decaying to WZ in the l nu l'l' (l = mu, e), llq (q) over bar, l nu q (q) over bar and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WZ bosons are compared with predictions of an extended gauge model with a heavy W' boson. In addition, direct searches for a neutral diboson resonance decaying to WW and ZZ in the llq (q) over bar, l nu q (q) over bar, and fully hadronic final states are combined and upper limits on the rate of production times branching ratio to the WW and ZZ bosons are compared with predictions for a heavy, spin-2 graviton in an extended Randall-Sundrum model where the Standard Model fields are allowed to propagate in the bulk of the extra dimension. (C) 2016 CERN for the benefit of the ATLAS Collaboration. Published by Elsevier B.V.
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Aristizabal Sierra, D., Herrero-Garcia, J., Restrepo, D., & Vicente, A. (2016). Diboson anomaly: Heavy Higgs resonance and QCD vectorlike exotics. Phys. Rev. D, 93(1), 015012–12pp.
Abstract: The ATLAS Collaboration (and also CMS) has recently reported an excess over Standard Model expectations for gauge boson pair production in the invariant mass region 1.8-2.2 TeV. In light of these results, we argue that such a signal might be the first manifestation of the production and further decay of a heavy CP-even Higgs resulting from a type-I two Higgs doublet model. We demonstrate that in the presence of colored vectorlike fermions, its gluon fusion production cross section is strongly enhanced, with the enhancement depending on the color representation of the new fermion states. Our findings show that barring the color triplet case, any QCD “exotic” representation can fit the ATLAS result in fairly large portions of the parameter space. We have found that if the diboson excess is confirmed and this mechanism is indeed responsible for it, then the LHC Run-2 should find (i) a CP-odd scalar with mass below similar to 2.3 TeV, (ii) new colored states with masses below similar to 2 TeV, (iii) no statistically significant diboson events in the W(+/-)Z channel, (iv) events in the triboson channels W(+/-)W(-/+)Z and ZZZ with invariant mass amounting to the mass of the CP-odd scalar.
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ATLAS TRT collaboration(Mindur, B. et al), Mitsou, V. A., & Valls Ferrer, J. A. (2016). Gas gain stabilisation in the ATLAS TRT detector. J. Instrum., 11, P04027–19pp.
Abstract: The ATLAS (one of two general purpose detectors at the LHC) Transition Radiation Tracker (TRT) is the outermost of the three tracking subsystems of the ATLAS Inner Detector. It is a large straw-based detector and contains about 350,000 electronics channels. The performance of the TRT as tracking and particularly particle identification detector strongly depends on stability of the operation parameters with most important parameter being the gas gain which must be kept constant across the detector volume. The gas gain in the straws can vary significantly with atmospheric pressure, temperature, and gas mixture composition changes. This paper presents a concept of the gas gain stabilisation in the TRT and describes in detail the Gas Gain Stabilisation System (GGSS) integrated into the Detector Control System (DCS). Operation stability of the GGSS during Run-1 is demonstrated.
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ANTARES Collaboration(Adrian-Martinez, S. et al), Barrios-Marti, J., Gomez-Gonzalez, J. P., Hernandez-Rey, J. J., Lambard, G., Mangano, S., et al. (2016). Time calibration with atmospheric muon tracks in the ANTARES neutrino telescope. Astropart Phys., 78, 43–51.
Abstract: The ANTARES experiment consists of an array of photomultipliers distributed along 12 lines and located deep underwater in the Mediterranean Sea. It searches for astrophysical neutrinos collecting the Cherenkov light induced by the charged particles, mainly muons, produced in neutrino interactions around the detector. Since at energies of similar to 10 TeV the muon and the incident neutrino are almost collinear, it is possible to use the ANTARES detector as a neutrino telescope and identify a source of neutrinos in the sky starting from a precise reconstruction of the muon trajectory. To get this result, the arrival times of the Cherenkov photons must be accurately measured. A to perform time calibrations with the precision required to have optimal performances of the instrument is described. The reconstructed tracks of the atmospheric muons in the ANTARES detector are used to determine the relative time offsets between photomultipliers. Currently, this method is used to obtain the time calibration constants for photomultipliers on different lines at a precision level of 0.5 ns. It has also been validated for calibrating photomultipliers on the same line, using a system of LEDs and laser light devices.
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