2,806 research outputs found

    The present and future status of heavy neutral leptons

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    Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereThe existence of nonzero neutrino masses points to the likely existence of multiple Standard Model neutral fermions. When such states are heavy enough that they cannot be produced in oscillations, they are referred to as heavy neutral leptons (HNLs). In this white paper, we discuss the present experimental status of HNLs including colliders, beta decay, accelerators, as well as astrophysical and cosmological impacts. We discuss the importance of continuing to search for HNLs, and its potential impact on our understanding of key fundamental questions, and additionally we outline the future prospects for next-generation future experiments or upcoming accelerator run scenario

    Design and performance of the ENUBET monitored neutrino beam

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    The ENUBET project is aimed at designing and experimentally demonstrating the concept of monitored neutrino beams. These novel beams are enhanced by an instrumented decay tunnel, whose detectors reconstruct large-angle charged leptons produced in the tunnel and give a direct estimate of the neutrino flux at the source. These facilities are thus the ideal tool for high-precision neutrino cross-section measurements at the GeV scale because they offer superior control of beam systematics with respect to existing facilities. In this paper, we present the first end-to-end design of a monitored neutrino beam capable of monitoring lepton production at the single particle level. This goal is achieved by a new focusing system without magnetic horns, a 20 m normal-conducting transfer line for charge and momentum selection, and a 40 m tunnel instrumented with cost-effective particle detectors. Employing such a design, we show that percent precision in cross-section measurements can be achieved at the CERN SPS complex with existing neutrino detectors

    Semianalytical and Numerical Studies of Relativistic Heavy Ion Collisions

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    The quark-gluon plasma (QGP) has been produced by relativistic heavy ion collisions, and understanding its properties is a primary goal in the field of nuclear physics. This research first elucidates recent semianalytical developments that improve the estimates of the initial energy and net conserved-charge densities and enable the calculation of trajectories in the quantum chromodynamics (QCD) phase diagram for the matter produced by nuclear collisions. A semianalytical model of the initial densities is developed by including the finite nuclear thickness for parton production. The new maximum energy density is found to have an analytical upper bound and satisfy an approximate scaling relation. QCD phase diagram trajectories are extracted from the semianalytical densities using several nuclear equations of state, and the calculated QGP lifetimes are found to depend significantly on the values of the model’s parameters. The study next presents a comparison between two solutions of the relativistic Boltzmann equation (RBE): one, a numerical solution using parton trans- port; the other, a theoretical solution for a homogeneous gas of massless particles. Parton transport in Zhang’s parton cascade (ZPC) is found to reproduce the results of a recent ex- act analytical solution of the RBE with an unexpected effectiveness at high densities when using new generalized collision schemes. Finally, the work discusses some open questions related to parton transport in ZPC and suggests some possible directions to uncover their answers. These future research goals include discovering the cause of an unexpected problem arising in simulations with three-dimensional (3D) expansion, understanding the theoretical distribution of the total center-of-mass (CM) energy squared for two-parton collisions, and studying curved parton motion in the presence of strong electromagnetic fields. Overall, the results presented in this dissertation improve the theoretical and numerical descriptions of the QGP and should be useful for future studies

    Development of a new silicon pixel detector with 10 ps time resolution for high luminosity future experiments

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    In this thesis work the results of the characterizations of the 3D-trench TimeSPOT silicon sensors with minimum ionizing particles are described. Such devices have been developed to satisfy the requirements of the LHCb VErtex LOcator detector for the Upgrade II, planned to face the high luminosity conditions. These requirements are a time resolution better than 50 ps per hit, a spatial resolution of the order of 10–20 μm and a radiation hardness up to 6·10^16 1 MeV n_eq/cm^2. In this thesis the characterizations performed both in the laboratory with a 90Sr source and in several test beam campaigns are illustrated. The main measurements done are the time resolution and the detection efficiency before and after the irradiation up to 2.5·10^16 1 MeV n_eq/cm^2

    Higgs boson pair production at NLO in the POWHEG approach and the top quark mass uncertainties

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    We present a new Monte Carlo code for Higgs boson pair production at next-to-leading order in the POWHEG-BOX Monte Carlo approach. The code is based on analytic results for the two loop virtual corrections which include the full top quark mass dependence. This feature allows to freely assign the value of all input parameters, including the trilinear Higgs boson self coupling, as well as to vary the renormalization scheme employed for the top quark mass. We study the uncertainties due to the top-mass renormalization scheme allowing the trilinear Higgs boson self coupling to vary around its Standard Model value including parton shower effects. Results are presented for both inclusive and differential observables.Comment: 21 pages, 7 figure

    Results on Elastic Cross Sections in Proton-Proton Collisions at s=510\sqrt{s} = 510 GeV with the STAR Detector at RHIC

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    We report results on an elastic cross section measurement in proton-proton collisions at a center-of-mass energy s=510\sqrt{s}=510 GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range 0.23≤−t≤0.670.23 \leq -t \leq 0.67~GeV2^2. We find that a constant slope BB does not fit the data in the aforementioned tt range, and we obtain a much better fit using a second-order polynomial for B(t)B(t). The tt dependence of BB is determined using six subintervals of tt in the STAR measured tt range, and is in good agreement with the phenomenological models. The measured elastic differential cross section dσ/dt\mathrm{d}\sigma/\mathrm{dt} agrees well with the results obtained at s=546\sqrt{s} = 546~GeV for proton--antiproton collisions by the UA4 experiment. We also determine that the integrated elastic cross section within the STAR tt-range is σelfid=462.1±0.9(stat.)±1.1(syst.)±11.6(scale)\sigma^\mathrm{fid}_\mathrm{el} = 462.1 \pm 0.9 (\mathrm{stat.}) \pm 1.1 (\mathrm {syst.}) \pm 11.6 (\mathrm {scale})~μb\mu\mathrm{b}.Comment: 9 pages, 9 figure

    Effect of Coriolis Force on Shear Viscosity : A Non-Relativistic Description

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    We have addressed that during the transition from zero to finite rotation picture, a transition from isotropic to anisotropic nature of shear viscosity coefficients can be found due to Coriolis force as expected due to Lorentz force at a finite magnetic field in earlier studies on the topics of relativistic matter like quark-gluon plasma. We have done it for non-relativistic matters for simplicity, with a future proposal to extend it towards a relativistic description. Introducing the Coriolis force term in relaxation time approximated Boltzmann transport equation, we have found different effective relaxation times along the parallel, perpendicular, and Hall directions in terms of actual relaxation time and rotating time period. Comparing the present formalism with the finite magnetic field picture, we have shown the equivalence of roles between the rotating and cyclotron time periods, which define the rotating time period as the inverse of 2 times angular velocity.Comment: 11 pages, 5 figures; For any comments or suggestions, emails are welcom

    Forward production of a Drell-Yan pair and a jet at small xx at next-to-leading order

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    We perform the analytical next-to-leading order calculation of the process p+A→γ∗+jet+Xp+A\to \gamma^{*}+\mathrm{jet}+X, at forward rapidities and low xx. These kinematics justify a hybrid approach, where a quark from the \textquoteleft projectile' proton scatters off the gluon distribution of the \textquoteleft target', which can be a nucleus or a highly boosted proton. By using the Color Glass Condensate effective theory approach, this gluon distribution is allowed to be so dense that the quark undergoes multiple scattering. Moreover, large high-energy logarithms in the ratio of the hard scale and the center-of-mass energy are resummed by the Balitsky, Kovchegov, Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov, Kovner or BK-JIMWLK evolution equations. We demonstrate that all ultraviolet divergences encountered in the calculation cancel, while the high-energy divergences are absorbed into BK-JIMWLK. The remaining singularities are collinear in nature and can be either absorbed into the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution of the incoming quark, when they stem from initial-state radiation, or else can be treated by introduction of a jet function in case they are caused by final-state emissions. The resulting cross section is completely finite and expressed in function of only a small set of color operators.Comment: 101 plus 17 pages (main text plus appendices and bibliography), 11 figure

    Higher Order QCD Studies of Semi-Inclusive Deep-Inelastic Scattering

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    In der vorliegenden Dissertation habe ich mich intensiv mit der Berechnung von Beiträgen zu Wirkungsquerschnitten der semi-inklusiven tiefinelastischen Streuung (SIDIS) beschäftigt. Die gewonnenen Ergebnisse können verwendet werden, um Informationen über die Partonverteilungsfunktionen und Fragmentationsfunktionen aus SIDIS-Daten zu erhalten. Sie tragen somit zur genaueren Bestimmung der Nukleonenstruktur bei. Insbesondere führen diese Erkenntnisse auch zu Informationen über die Spinstruktur des Protons. Im Rahmen der perturbativen Quantenchromodynamik wurden Beiträge zur Störungsreihe der transversalen Strukturfunktion in SIDIS untersucht, welche in allen Ordnungen der laufenden starken Kopplung auftreten. Dieses Phänomen, bekannt als threshold resummation, taucht in der Region des Phasenraums auf, in der logarithmische Beiträge zu einer festen Ordnung divergieren. Das Summieren jener logarithmischen Beiträge in allen Ordnungen liefert schließlich endliche Beiträge zur Strukturfunktion. Das Wissen über den Aufbau solcher Beiträge ermöglicht, sie zu einer beliebigen festen Ordnung vorherzusagen. Somit ist eine Näherung der Strukturfunktion in einer festen Ordnung durch sogenannte threshold-Logarithmen möglich. Ziel der vorliegenden Dissertation ist, es eine Näherung der transversalen Strukturfunktion in übernächst-führender Ordnung durch threshold-Logarithmen zu erhalten. Dabei wurden außerdem (führende) Beiträge berücksichtigt, welche in der threshold-Region des Phasenraums unterdrückt sind. Im letzten Teil der Dissertation wird das Verhalten der SIDIS Strukturfunktionen zur Streuung von longitudinal polarisierten Protonen mit unpolarisierten Elektro nen bei kleinen Transversalimpulsen untersucht. In diesem Bereich können SIDIS- Daten besonders gut durch transversalimpulsabhängige Partonverteilungsfunkti onen beschrieben werden. Hier wird der Kontakt zu jenen Verteilungsfunktionen von Seiten der kollinearen Faktorisierung hergestellt und die sogenannte T-odd- Asymmetrie im Limes kleiner Transversalimpulse betrachtet
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