1,693 research outputs found

    Analysis of J/Psi production with the CMS detector at the Large Hadron Collider

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    The J/psi particle is a vector meson with a mass of 3096.916¬Ī0.011 MeV. It has been observed in 1974 by two experiments at Stanford and Brookhaven, and is the first bound state of a charm quark and an anticharm quark ever discovered in the history of particle physics. Differently from lighter quarks, the charm quark is characterized by a rest mass significantly greater than the typical energy scale of Quantum Chromo Dynamics processes, which take place during the binding of the meson. This greater mass results in its constituent quarks being relatively "slow" inside it, justifying a non-relativistic description of its production process. The J/psi, along with other charm-anticharm bound states, represents an important laboratory where the theoretical models of the strong interaction are verified. Heavy mesons are produced in copious amounts in high energy proton-proton collisions, and the recent beginning of experiments at the CERN Large Hadron Collider has given an opportunity to study the behavior of J/psi production at a center-of-mass energy of 7 TeV with the CMS detector. This detector has been designed as a general-purpose one and is capable of good performance in this kinds of studies, especially in the J/psi to mu+ mu- decay channel. Indeed, the past 20 years have seen a revival of interest in the study of the production process of the J/psi. A measurement performed by the CDF experiment in 1992-1993 at the Tevatron p-pbar collider found the production cross-section to be larger than the theoretical prediction by a factor of 50. Consequently, the model in use at the time - the Color Singlet Model - had to be abandoned in favor of a Non-Relativistic QCD description called the Color Octet Model. Recently, also this model has been put into discussion, as the predictions it makes on the polarization of the J/psi seem not to match experimental data by the E866, HERA-B and CDF II experiments, and even more puzzling is the fact that the E866 and HERA-B measurement are inconsistent. A possible explanation of these inconsistencies may be hidden in the different experimental conditions under which these experiments took place (mainly, the detector acceptances), and the fact that the measurements were performed in different frames of reference. Once identified the importance of the cross-section and polarization measurements, I present the cross-section measurement performed on data taken in 2010 with the CMS detector and present the ongoing effort in measuring the J/psi polarization by the CMS collaboration - in which I have worked as a student for the purpose of this thesis. In my thesis I introduce a frame-invariant approach which should overcome these elements and provide a clear picture of the behavior of the polarization (longitudinal, transverse or a combination of these states) as a function of transverse momentum. The measurement requires a series of introductory steps aimed at understanding all aspects of detector response to muons, among them is the calculation of the detector acceptance for the muon pairs with Monte Carlo simulations, the study based on real data of the tracking efficiency, that of muon identification efficiency and that of trigger efficiency, the latter being one of my responsibilities during my work. The efficiency study has been performed by the use of the "Tag and Probe" method for resonances decaying to dimuons, where a muon of the pair is required to pass a series of very tight cuts. The pairs surviving this extreme skimming have the other muon analyzed, in order to perform a statistical measurement on the relevant variable

    OpenIPMC: a free and open source Intelligent Platform Management Controller

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    OpenIPMC is a free and open source firmware designed to operate as an Intelligent Platform Management Controller (IPMC). An IPMC is a fundamental component of electronic boards conformant to the Advanced Telecommunications Computing Architecture (ATCA) standard, currently being adopted by a number of high energy physics experiments, and is responsible for monitoring the health parameters of the board, managing its power states, and providing board control, debug and recovery functions to remote clients. OpenIPMC is based on the FreeRTOS real-time operating system and is designed to be architecture-independent, allowing it to be built for a variety of different Microcontrollers. Having a fully free and open source code is an innovative aspect for this kind of firmware, allowing full customization by the user. In this work we present the features and structure of OpenIPMC and its example implementations on Xilinx Zynq UltraScale+ (ZynqUS+), Espressif ESP32, and ST Microelectronics STM32 architectures.Comment: 8 pages, double-column, 9 figures, 2 tables. Paper submitted as proceeding for the IEEE Real-Time 2020 conferenc

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an