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Aliaga, R. J. (2017). Real-Time Estimation of Zero Crossings of Sampled Signals for Timing Using Cubic Spline Interpolation. IEEE Trans. Nucl. Sci., 64(8), 2414–2422.
Abstract: A scheme is proposed for hardware estimation of the location of zero crossings of sampled signals with subsample resolution for timing applications, which consists of interpolating the signal with a cubic spline near the zero crossing and then finding the root of the resulting polynomial. An iterative algorithm based on the bisection method is presented that obtains one bit of the result per step and admits an efficient digital implementation using fixed-point representation. In particular, the root estimation iteration involves only two additions, and the initial values can be obtained from finite impulse response (FIR) filters with certain symmetry properties. It is shown that this allows online real-time estimation of timestamps in free-running sampling detector systems with improved accuracy with respect to the more common linear interpolation. The method is evaluated with simulations using ideal and real timing signals, and estimates are given for the resource usage and speed of its implementation.
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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). Reconstruction of primary vertices at the ATLAS experiment in Run 1 proton-proton collisions at the LHC. Eur. Phys. J. C, 77(5), 332–35pp.
Abstract: This paper presents the method and performance of primary vertex reconstruction in proton-proton collision data recorded by the ATLAS experiment during Run 1 of the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of root s = 8 TeV. The performance has been measured as a function of the number of interactions per bunch crossing over a wide range, from one to seventy. The measurement of the position and size of the luminous region and its use as a constraint to improve the primary vertex resolution are discussed. A longitudinal vertex position resolution of about 30 μm is achieved for events with high multiplicity of reconstructed tracks. The transverse position resolution is better than 20 μm and is dominated by the precision on the size of the luminous region. An analytical model is proposed to describe the primary vertex reconstruction efficiency as a function of the number of interactions per bunch crossing and of the longitudinal size of the luminous region. Agreement between the data and the predictions of this model is better than 3% up to seventy interactions per bunch crossing.
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Rinaldi, M., & Ceccopieri, F. A. (2017). Relativistic effects in model calculations of double parton distribution functions. Phys. Rev. D, 95(3), 034040–9pp.
Abstract: In this paper we consider double-parton distribution functions (dPDFs), which are the main nonperturbative ingredients appearing in the double-parton scattering cross section formula in hadronic collisions. By using recent calculation of dPDFs by means of constituent quark models within the so-called light-front approach, we investigate the role of relativistic effects on dPDFs. We find, in particular, that the so-called Melosh operators, which allow us to properly convert the LF spin into the canonical one and incorporate a proper treatment of boosts, produce sizeable effects on dPDFs. We discuss specific partonic correlations induced by these operators in the transverse plane which are relevant to the proton structure, and we study under which conditions these results are stable against variations in the choice of the proton wave function.
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Kim, C. S., Lopez-Castro, G., Tostado, S. L., & Vicente, A. (2017). Remarks on the Standard Model predictions for R(D) and R(D*). Phys. Rev. D, 95(1), 013003–7pp.
Abstract: Semileptonic b -> c transitions, and in particular the ratios R(D-(*())) = Gamma(B -> D-(*())tau nu)/Gamma(B -> D-(*())l nu), can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by the BABAR, Belle, and LHCb collaborations and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that R(D) might be enhanced by lepton mass effects associated to the mostly unknown scalar form factor. In contrast, the Standard Model prediction for R(D*) is found to be more robust, because possible pollutions from B* contributions turn out to be negligibly small; this indicates that R(D) is a promising observable for searches of new physics.
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XENON Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2017). Removing krypton from xenon by cryogenic distillation to the ppq level. Eur. Phys. J. C, 77(5), 275–12pp.
Abstract: The XENON1T experiment aims for the direct detection of dark matter in a detector filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by radioactive decays inside the detector has to be sufficiently low. One major contributor is the beta-emitter Kr-85 which is present in the xenon. For XENON1T a concentration of natural krypton in xenon Kr-nat/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10(-15) mol/mol) is required. In this work, the design, construction and test of a novel cryogenic distillation column using the common McCabe-Thiele approach is described. The system demonstrated a krypton reduction factor of 6.4 . 10(5) with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of natKr/Xe < 26 ppq is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN.
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Chatterjee, S. S., Pasquini, P., & Valle, J. W. F. (2017). Resolving the atmospheric octant by an improved measurement of the reactor angle. Phys. Rev. D, 96(1), 011303–6pp.
Abstract: Taking into account the current global information on neutrino oscillation parameters we forecast the capabilities of future long-baseline experiments such as DUNE and T2HK in settling the atmospheric octant puzzle. We find that a good measurement of the reactor angle theta(13) plays a key role in fixing the octant of the atmospheric angle theta(23) with such future accelerator neutrino studies.
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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). Resonances and CP violation in B-s(0) and (B)over-bar(s)(0) -> j psi K+K- decays in the mass region above the I center dot(1020). J. High Energy Phys., 08(8), 037–28pp.
Abstract: The decays of B (s) (0) and mesons into the J/psi K (+) K (-) final state are studied in the K (+) K (-) mass region above the I center dot(1020) meson in order to determine the resonant substructure and measure the CP-violating phase, I center dot (s) , the decay width, I“ (s) , and the width difference between light and heavy mass eigenstates, Delta I” (s) . A decay-time dependent amplitude analysis is employed. The data sample corresponds to an integrated luminosity of 3 fb(-1) produced in 7 and 8 TeV pp collisions at the LHC, collected by the LHCb experiment. The measurement determines I center dot (s) = 119 +/- 107 +/- 34 mrad. A combination with previous LHCb measurements using similar decays into the J/psi pi (+) pi (-) and J/psi I center dot(1020) final states gives I center dot (s) = 1 +/- 37 mrad, consistent with the Standard Model prediction.
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XENON Collaboration(Aprile, E. et al), & Orrigo, S. E. A. (2017). Results from a calibration of XENON100 using a source of dissolved radon-220. Phys. Rev. D, 95(7), 072008–10pp.
Abstract: A Rn-220 source is deployed on the XENON100 dark matter detector in order to address the challenges in calibration of tonne-scale liquid noble element detectors. We show that the Pb-212 beta emission can be used for low-energy electronic recoil calibration in searches for dark matter. The isotope spreads throughout the entire active region of the detector, and its activity naturally decays below background level within a week after the source is closed. We find no increase in the activity of the troublesome Rn-222 background after calibration. Alpha emitters are also distributed throughout the detector and facilitate calibration of its response to Rn-222. Using the delayed coincidence of Rn-220-Po-216, we map for the first time the convective motion of particles in the XENON100 detector. Additionally, we make a competitive measurement of the half-life of Po-212, t(1/2) = (293.9 +/- (1.0)(stat) +/- (0.6)(sys)) ns.
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ANTARES Collaboration(Albert, A. et al), Barrios-Marti, J., Hernandez-Rey, J. J., Illuminati, G., Lotze, M., Tönnis, C., et al. (2017). Results from the search for dark matter in the Milky Way with 9 years of data of the ANTARES neutrino telescope. Phys. Lett. B, 769, 249–254.
Abstract: Using data recorded with the ANTARES telescope from 2007 to 2015, a new search for dark matter annihilation in the Milky Way has been performed. Three halo models and five annihilation channels, WIMP + WIMP -> b (b) over bar, W+W-, tau(+)tau(-), mu(+)mu(-) and v (v) over bar, with WIMP masses ranging from 50 2 GeV/C-2 to 100 Tev/C-2, were considered. No excess over the expected background was found, and limits on the thermally averaged annihilation cross-section were set.
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Barenboim, G., Kinney, W. H., & Park, W. I. (2017). Resurrection of large lepton number asymmetries from neutrino flavor oscillations. Phys. Rev. D, 95(4), 043506–6pp.
Abstract: We numerically solve the evolution equations of neutrino three-flavor density matrices, and show that, even if neutrino oscillations mix neutrino flavors, large lepton number asymmetries are still allowed in certain limits by big bang nucleosynthesis.
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