Ortiz Arciniega, J. L., Carrio, F., & Valero, A. (2019). FPGA implementation of a deep learning algorithm for real-time signal reconstruction in particle detectors under high pile-up conditions. J. Instrum., 14, P09002–13pp.
Abstract: The analog signals generated in the read-out electronics of particle detectors are shaped prior to the digitization in order to improve the signal to noise ratio (SNR). The real amplitude of the analog signal is then obtained using digital filters, which provides information about the energy deposited in the detector. The classical digital filters have a good performance in ideal situations with Gaussian electronic noise and no pulse shape distortion. However, high-energy particle colliders, such as the Large Hadron Collider (LHC) at CERN, can produce multiple simultaneous events, which produce signal pileup. The performance of classical digital filters deteriorates in these conditions since the signal pulse shape gets distorted. In addition, this type of experiments produces a high rate of collisions, which requires high throughput data acquisitions systems. In order to cope with these harsh requirements, new read-out electronics systems are based on high-performance FPGAs, which permit the utilization of more advanced real-time signal reconstruction algorithms. In this paper, a deep learning method is proposed for real-time signal reconstruction in high pileup particle detectors. The performance of the new method has been studied using simulated data and the results are compared with a classical FIR filter method. In particular, the signals and FIR filter used in the ATLAS Tile Calorimeter are used as benchmark. The implementation, resources usage and performance of the proposed Neural Network algorithm in FPGA are also presented.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Measurement of jet-substructure observables in top quark, W boson and light jet production in proton-proton collisions at root s=13 TeV with the ATLAS detector. J. High Energy Phys., 08(8), 33–47pp.
Abstract: A measurement of jet substructure observables is presented using data collected in 2016 by the ATLAS experiment at the LHC with proton-proton collisions at root s= 13 TeV. Large-radius jets groomed with the trimming and soft-drop algorithms are studied. Dedicated event selections are used to study jets produced by light quarks or gluons, and hadronically decaying top quarks and W bosons. The observables measured are sensitive to substructure, and therefore are typically used for tagging large-radius jets from boosted massive particles. These include the energy correlation functions and the N-subjettiness variables. The number of subjets and the Les Houches angularity are also considered. The distributions of the substructure variables, corrected for detector effects, are compared to the predictions of various Monte Carlo event generators. They are also compared between the large-radius jets originating from light quarks or gluons, and hadronically decaying top quarks and W bosons.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of the Mass Difference Between Neutral Charm-Meson Eigenstates. Phys. Rev. Lett., 122(23), 231802–10pp.
Abstract: We report a measurement of the mass difference between neutral charm-meson eigenstates using a novel approach that enhances sensitivity to this parameter. We use 2.3 x 10(6) D-0 -> K-S(0)pi(+)pi(-) decays reconstructed in proton-proton collisions collected by the LHCb experiment in 2011 and 2012. Allowing for CP violation in mixing and in the interference between mixing and decay, we measure the CP-averaged normalized mass difference x(cp)= [2.7 +/- 1.6(stat) +/- 0.4(syst)] x 10(-3) and the CP-violating parameter Delta x = [-0.53 +/- 0.70(stat) +/- 0.22(syst)] x 10(-3). The results are consistent with CP symmetry. These determinations are the most precise from a single experiment and, combined with current world-average results, yield the fast evidence that the masses of the neutral charm-meson eigenstates differ.
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Mandal, S., Srivastava, R., & Valle, J. W. F. (2020). Consistency of the dynamical high-scale type-I seesaw mechanism. Phys. Rev. D, 101(11), 115030–15pp.
Abstract: We analyze the consistency of electroweak breaking within the simplest high-scale SU(3)(c) circle times SU(2)(L) circle times U(1)(Y) type-I seesaw mechanism. We derive the full two-loop renormalization group equations of the relevant parameters, including the quartic Higgs self-coupling of the Standard Model. For the simplest case of bare “right-handed” neutrino mass terms we find that, with large Yukawa couplings, the Higgs quartic self-coupling becomes negative much below the seesaw scale, so that the model may be inconsistent even as an effective theory. We show, however, that the “dynamical” type-I high-scale seesaw with spontaneous lepton number violation has better stability properties.
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Yokoyama, R., Singh, M., Grzywacz, R., Keeler, A., King, T. T., Agramunt, J., et al. (2019). Segmented YSO scintillation detectors as a new beta-implant detection tool for decay spectroscopy in fragmentation facilities. Nucl. Instrum. Methods Phys. Res. A, 937, 93–97.
Abstract: A newly developed segmented YSO scintillator detector was implemented for the first time at the RI-beam Factory at RIKEN Nishina Center as an implantation-decay counter. The results from the experiment demonstrate that the detector is a viable alternative to conventional silicon-strip detectors with its good timing resolution and high detection efficiency for beta particles. A Position-Sensitive Photo-Multiplier Tube (PSPMT) is coupled with a 48 x 48 segmented YSO crystal. To demonstrate its capabilities, a known short-lived isomer in Ni-76 and the beta decay of Co-74 were measured by implanting those ions into the YSO detector. The half-lives and gamma-rays observed in this work are consistent with the known values. The beta-ray detection efficiency is more than 80 % for the decay of Co-74.
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Papoulias, D. K., Kosmas, T. S., Sahu, R., Kota, V. K. B., & Hota, M. (2020). Constraining nuclear physics parameters with current and future COHERENT data. Phys. Lett. B, 800, 135133–9pp.
Abstract: Motivated by the recent observation of coherent elastic neutrino-nucleus scattering (CE nu NS) at the COHERENT experiment, our goal is to explore its potential in probing important nuclear structure parameters. We show that the recent COHERENT data offers unique opportunities to investigate the neutron nuclear form factor. Our present calculations are based on the deformed Shell Model (DSM) method which leads to a better fit of the recent CE nu NS data, as compared to known phenomenological form factors such as the Helm-type, symmetrized Fermi and Klein-Nystrand. The attainable sensitivities and the prospects of improvement during the next phase of the COHERENT experiment are also considered and analyzed in the framework of two upgrade scenarios.
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Alimena, J. et al, Hirsch, M., Mamuzic, J., Mitsou, V. A., & Santra, A. (2020). Searching for long-lived particles beyond the Standard Model at the Large Hadron Collider. J. Phys. G, 47(9), 090501–226pp.
Abstract: Particles beyond the Standard Model (SM) can generically have lifetimes that are long compared to SM particles at the weak scale. When produced at experiments such as the Large Hadron Collider (LHC) at CERN, these long-lived particles (LLPs) can decay far from the interaction vertex of the primary proton-proton collision. Such LLP signatures are distinct from those of promptly decaying particles that are targeted by the majority of searches for new physics at the LHC, often requiring customized techniques to identify, for example, significantly displaced decay vertices, tracks with atypical properties, and short track segments. Given their non-standard nature, a comprehensive overview of LLP signatures at the LHC is beneficial to ensure that possible avenues of the discovery of new physics are not overlooked. Here we report on the joint work of a community of theorists and experimentalists with the ATLAS, CMS, and LHCb experiments-as well as those working on dedicated experiments such as MoEDAL, milliQan, MATHUSLA, CODEX-b, and FASER-to survey the current state of LLP searches at the LHC, and to chart a path for the development of LLP searches into the future, both in the upcoming Run 3 and at the high-luminosity LHC. The work is organized around the current and future potential capabilities of LHC experiments to generally discover new LLPs, and takes a signature-based approach to surveying classes of models that give rise to LLPs rather than emphasizing any particular theory motivation. We develop a set of simplified models; assess the coverage of current searches; document known, often unexpected backgrounds; explore the capabilities of proposed detector upgrades; provide recommendations for the presentation of search results; and look towards the newest frontiers, namely high-multiplicity 'dark showers', highlighting opportunities for expanding the LHC reach for these signals.
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ATLAS Collaboration(Aaboud, M. et al), Alvarez Piqueras, D., Aparisi Pozo, J. A., Bailey, A. J., Barranco Navarro, L., Cabrera Urban, S., et al. (2019). Measurement of VH, H -> b(b)over-barproduction as a function of the vector-boson transverse momentum in 13 TeV pp collisions with the ATLAS detector. J. High Energy Phys., 05(5), 141–36pp.
Abstract: Cross-sections of associated production of a Higgs boson decaying into bottomquark pairs and an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum. The measurements are performed in kinematic fiducial volumes defined in the simplified template cross-section' framework. The results are obtained using 79.8 fb(-1) of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. All measurements are found to be in agreement with the Standard Model predictions, and limits are set on the parameters of an effective Lagrangian sensitive to modifications of the Higgs boson couplings to the electroweak gauge bosons.
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Molina, R., Geng, L. S., & Oset, E. (2019). Comments on the dispersion relation method to vector-vector interaction. Prog. Theor. Exp. Phys., (10), 103B05–16pp.
Abstract: We study in detail the method proposed recently to study the vector-vector interaction using the N/D method and dispersion relations, which concludes that, while, for J = 0, one finds bound states, in the case of J = 2, where the interaction is also attractive and much stronger, no bound state is found. In that work, approximations are done for N and D and a subtracted dispersion relation for D is used, with subtractions made up to a polynomial of second degree in s – s(th), matching the expression to 1 – VG at threshold. We study this in detail for the rho rho interaction and to see the convergence of the method we make an extra subtraction matching 1 – VG at threshold up to (s – s(th))(3). We show that the method cannot be used to extrapolate the results down to 1270 MeV where the f(2)(1270) resonance appears, due to the artificial singularity stemming from the “on-shell” factorization of the rho exchange potential. In addition, we explore the same method but folding this interaction with the mass distribution of the rho, and we show that the singularity disappears and the method allows one to extrapolate to low energies, where both the (s – s(th))(2) and (s – s(th))(3) expansions lead to a zero of Re D(s), at about the same energy where a realistic approach produces a bound state. Even then, the method generates a large Im D(s) that we discuss is unphysical.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). Measurement of the CP-violating phase phi(s) from B-s(0) -> J/psi pi(+)pi(-) decays in 13 TeV pp collisions. Phys. Lett. B, 797, 134789–12pp.
Abstract: Decays of B-s(0) and (B) over bar (0)(s) mesons into J/psi pi(+)pi(-) final states are studied in a data sample corresponding to 1.9 fb(-1) of integrated luminosity collected with the LHCb detector in 13 TeV pp collisions. A time-dependent amplitude analysis is used to determine the final-state resonance contributions, the CP-violating phase phi(s) = -0.057 +/- 0.060 +/- 0.011 rad, the decay-width difference between the heavier mass B-s(0) eigenstate and the B-0 meson of -0.050 +/- 0.004 +/- 0.004 ps(-1), and the CP-violating parameter vertical bar lambda vertical bar = 1.01(-0.06)(+0.08) +/- 0.03, where the first uncertainty is statistical and the second systematic. These results are combined with previous LHCb measurements in the same decay channel using 7 TeV and 8 TeV pp collisions obtaining phi(s) = 0.002 +/- 0.044 +/- 0.012 rad, and vertical bar lambda vertical bar = 0.949 +/- 0.036 +/- 0.019.
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