
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., MartinezVidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2019). Measurement of the CharmMixing Parameter y(CP). Phys. Rev. Lett., 122(1), 011802–10pp.
Abstract: A measurement of the charmmixing parameter YCP using D0 > K+K, D0 > pi(+)pi(), and D0 > Kpi(+)decays is reported. The D0 mesons are required to originate from semimuonic decays of B and (B) over bar (0)mesons. These decays are partially reconstructed in a data set of protonproton collisions at centerofmass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb(1). The y c p parameter is measured to be (0.57 +/ 0.13(stat) +/ 0.09(syst))%, in agreement with, and as precise as, the current worldaverage value.


Soderstrom, P. A. et al, Agramunt, J., Egea, J., Gadea, A., & Huyuk, T. (2019). Neutron detection and gammaray suppression using artificial neural networks with the liquid scintillators BC501A and BC537. Nucl. Instrum. Methods Phys. Res. A, 916, 238–245.
Abstract: In this work we present a comparison between the two liquid scintillators BC501A and BC537 in terms of their performance regarding the pulseshape discrimination between neutrons and gamma rays. Special emphasis is put on the application of artificial neural networks. The results show a systematically higher gammaray rejection ratio for BC501A compared to BC537 applying the commonly used charge comparison method. Using the artificial neural network approach the discrimination quality was improved to more than 95% rejection efficiency of gamma rays over the energy range 150 to 1000 keV for both BC501A and BC537. However, due to the larger light output of BC501A compared to BC537, neutrons could be identified in BC501A using artificial neural networks down to a recoil proton energy of 800 keV compared to a recoil deuteron energy of 1200 keV for BC537. We conclude that using artificial neural networks it is possible to obtain the same gammaray rejection quality from both BC501A and BC537 for neutrons above a lowenergy threshold. This threshold is, however, lower for BC501A, which is important for nuclear structure spectroscopy experiments of rare reaction channels where lowenergy interactions dominates.
Keywords: BC501A; BC537; Digital pulseshape discrimination; Fastneutron detection; Liquid scintillator; Neural networks


Alvarez, V., HerreroBosch, V., Esteve, R., Laing, A., Rodriguez, J., Querol, M., et al. (2019). The electronics of the energy plane of the NEXTWhite detector. Nucl. Instrum. Methods Phys. Res. A, 917, 68–76.
Abstract: This paper describes the electronics of NEXTWhite (NEW) detector PMT plane, a high pressure xenon TPC with electroluminescent amplification (HPXeEL) currently operating at the Laboratorio Subterraneo de Canfranc (LSC) in Huesca, Spain. In NEXTWhite the energy of the event is measured by a plane of photomultipliers (PMTs) located behind a transparent cathode. The PMTs are Hamamatsu R1141010 chosen due to their low radioactivity. The electronics have been designed and implemented to fulfill strict requirements: an overall energy resolution below 1% and a radiopurity budget of 20 mBq unit(1) in the chain of Bi214. All the components and materials have been carefully screened to assure a low radioactivity level and at the same time meet the required frontend electronics specifications. In order to reduce low frequency noise effects and enhance detector safety a grounded cathode connection has been used for the PMTs. This implies an ACcoupled readout and baseline variations in the PMT signals. A detailed description of the electronics and a novel approach based on a digital baseline restoration to obtain a linear response and handle AC coupling effects is presented. The final PMT channel design has been characterized with linearity better than 0.4% and noise below 0.4 mV.
Keywords: Calorimetry; Frontend electronics; Digital baseline restoration


Debastiani, V. R., & Navarra, F. S. (2019). A nonrelativistic model for the [cc][(c)overbar(c)overbar] tetraquark. Chin. Phys. C, 43(1), 013105–20pp.
Abstract: We use a nonrelativistic model to study the spectroscopy of a tetraquark composed of [cc][(c) over bar(c) over bar] in a diquarkantidiquark configuration. By numerically solving the Schrodinger equation with a Cornellinspired potential, we separate the fourbody problem into three twobody problems. Spindependent terms (spinspin, spinorbit and tensor) are used to describe the splitting structure of the c (c) over bar spectrum and are also extended to the interaction between diquarks. Recent experimental data on charmonium states are used to fix the parameters of the model and a satisfactory description of the spectrum is obtained. We find that the spindependent interaction is sizable in the diquarkantidiquark system, despite the heavy diquark mass, and also that the diquark has a finite size if treated in the same way as the c (c) over bar systems. We find that the lowest Swave T4c tetraquarks might be below their thresholds of spontaneous dissociation into lowlying charmonium pairs, while orbital and radial excitations would be mostly above the corresponding charmonium pair thresholds. Finally, we repeat the calculations without the confining part of the potential and obtain bound diquarks and bound tetraquarks. This might be relevant to the study of exotic charmonium in the quarkgluon plasma. The T4c states could be investigated in the forthcoming experiments at the LHC and Belle II.
Keywords: tetraquark; charmonium; diquarkantidiquark; nonrelativistic; spin


Heisenberg, L., Ramirez, H., & Tsujikawa, S. (2019). Inflation with mixed helicities and its observational imprint on CMB. Phys. Rev. D, 99(2), 023505–14pp.
Abstract: In the framework of effective field theories with prominent helicity0 and helicity1 fields coupled to each other via a dimension3 operator, we study the dynamics of inflation driven by the helicity0 mode, with a given potential energy, as well as the evolution of cosmological perturbations, influenced by the presence of a mixing term between both helicities. In this scenario, the temporal component of the helicity1 mode is an auxiliary field and can be integrated out in terms of the time derivative of the helicity0 mode, so that the background dynamics effectively reduces to that in singlefield inflation modulated by a parameter beta associated to the coupling between helicity0 and helicity1 modes. We discuss the evolution of a longitudinal scalar perturbation psi and an inflaton fluctuation delta phi, and we explicitly show that a particular combination of these two, which corresponds to an isocurvature mode, is subject to exponential suppression by the vector mass comparable to the Hubble expansion rate during inflation. Furthermore, we find that the effective singlefield description corrected by beta also holds for the power spectrum of curvature perturbations generated during inflation. We compute the standard inflationary observables such as the scalar spectral index n(s), and the tensortoscalar ratio r and confront several inflaton potentials with the recent observational data provided by Planck 2018. Our results show that the coupling between helicity0 and helicity1 modes can lead to a smaller value of the tensortoscalar ratio especially for smallfield inflationary models, so our scenario exhibits even better compatibility with the current observational data.


