Search for New Physics in Pp Collisions at 7 TeV Center-of-mass Energy Using Diphoton Events with Large Missing Transverse Energy in the CMS Experiment at the LHC PDF Download

Author: Robert Wayne Stringer
Publisher:
ISBN: 9781124771816
Category : Gauge fields (Physics)
Languages : en
Pages : 176

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Book Description
Many theoretical models of physics beyond the Standard Model provide a signature of two photons and large missing transverse energy [Special characters omitted.] in the final state. This search was performed using 36 pb[superscript -1] of proton-proton collision data at [Squared root of s] = 7 TeV. The candidate events are determined by comparing the [Special characters omitted.] distribution for events with two photons and at least one hadronic jet with the [Special characters omitted.] T distribution from QCD and electroweak processes that have no true missing transverse energy. 1.2 ± 0.8 background events were expected, with one event observed. This result was interpreted in two theoretical models beyond the Standard Model. The cross section for General Gauge Mediated Supersymmetry Breaking is given an upper limit between 0.3 pb and 1.1 pb. Universal Extra Dimensions has been excluded for all values of 1/ R

Author: Herwig Schopper
Publisher: Springer Nature
ISBN: 3030382079
Category : Heavy ions
Languages : en
Pages : 632

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Book Description
This first open access volume of the handbook series contains articles on the standard model of particle physics, both from the theoretical and experimental perspective. It also covers related topics, such as heavy-ion physics, neutrino physics and searches for new physics beyond the standard model. A joint CERN-Springer initiative, the "Particle Physics Reference Library" provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A, B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access

Author: Simone Marzani
Publisher: Springer
ISBN: 3030157091
Category : Science
Languages : en
Pages : 205

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Book Description
This concise primer reviews the latest developments in the field of jets. Jets are collinear sprays of hadrons produced in very high-energy collisions, e.g. at the LHC or at a future hadron collider. They are essential to and ubiquitous in experimental analyses, making their study crucial. At present LHC energies and beyond, massive particles around the electroweak scale are frequently produced with transverse momenta that are much larger than their mass, i.e., boosted. The decay products of such boosted massive objects tend to occupy only a relatively small and confined area of the detector and are observed as a single jet. Jets hence arise from many different sources and it is important to be able to distinguish the rare events with boosted resonances from the large backgrounds originating from Quantum Chromodynamics (QCD). This requires familiarity with the internal properties of jets, such as their different radiation patterns, a field broadly known as jet substructure. This set of notes begins by providing a phenomenological motivation, explaining why the study of jets and their substructure is of particular importance for the current and future program of the LHC, followed by a brief but insightful introduction to QCD and to hadron-collider phenomenology. The next section introduces jets as complex objects constructed from a sequential recombination algorithm. In this context some experimental aspects are also reviewed. Since jet substructure calculations are multi-scale problems that call for all-order treatments (resummations), the bases of such calculations are discussed for simple jet quantities. With these QCD and jet physics ingredients in hand, readers can then dig into jet substructure itself. Accordingly, these notes first highlight the main concepts behind substructure techniques and introduce a list of the main jet substructure tools that have been used over the past decade. Analytic calculations are then provided for several families of tools, the goal being to identify their key characteristics. In closing, the book provides an overview of LHC searches and measurements where jet substructure techniques are used, reviews the main take-home messages, and outlines future perspectives.

Author: Hongliang Liu
Publisher:
ISBN: 9781267132529
Category : Gauge invariance
Languages : en
Pages : 160

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Book Description
We perform a search for long-lived neutral particles decaying into a photon and invisible particles in pp collisions at a center-of-mass energy of 7 TeV at the Large Hadron Collider. In the context of gauge mediated supersymmetry with the lightest neutralino as the next-to-lightest supersymmetric particle and the gravitino as the lightest supersymmetric particle, the neutralino can decay into a gravitino and a photon with a non-zero lifetime. The impact parameter of the photon relative to the beam-beam collision point can be reconstructed using converted photons. The method is sensitive to lifetimes of the order of [Special characters omitted.] (0.1 ns). The data sample corresponds to an integrated luminosity of 2.1 ± 0.1 fb -1 recorded in the first part of 2011 by the CMS experiment at the LHC at [Special characters omitted.] = 7 TeV. The search is performed using events containing photons, missing transverse energy and jets. Upper limits at the 95% confidence level are presented on the cross section for such particles from pair-production, each of which decays into a photon and invisible particles.

Author: Christian W. Fabjan
Publisher: Springer Nature
ISBN: 3030353184
Category : Elementary particles (Physics).
Languages : en
Pages : 1083

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Book Description
This second open access volume of the handbook series deals with detectors, large experimental facilities and data handling, both for accelerator and non-accelerator based experiments. It also covers applications in medicine and life sciences. A joint CERN-Springer initiative, the "Particle Physics Reference Library" provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A, B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access

Author: Yueh-Feng Liu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description

Author: Aleandro Nisati
Publisher: World Scientific
ISBN: 981442546X
Category : Science
Languages : en
Pages : 470

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Book Description
The recent observation of the Higgs boson has been hailed as the scientific discovery of the century and led to the 2013 Nobel Prize in physics. This book describes the detailed science behind the decades-long search for this elusive particle at the Large Electron Positron Collider at CERN and at the Tevatron at Fermilab and its subsequent discovery and characterization at the Large Hadron Collider at CERN. Written by physicists who played leading roles in this epic search and discovery, this book is an authoritative and pedagogical exposition of the portrait of the Higgs boson that has emerged from a large number of experimental measurements. As the first of its kind, this book should be of interest to graduate students and researchers in particle physics.

Author: Tilman Plehn
Publisher: Springer
ISBN: 3319059424
Category : Science
Languages : en
Pages : 340

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Book Description
With the discovery of the Higgs boson, the LHC experiments have closed the most important gap in our understanding of fundamental interactions, confirming that such interactions between elementary particles can be described by quantum field theory, more specifically by a renormalizable gauge theory. This theory is a priori valid for arbitrarily high energy scales and does not require an ultraviolet completion. Yet, when trying to apply the concrete knowledge of quantum field theory to actual LHC physics - in particular to the Higgs sector and certain regimes of QCD - one inevitably encounters an intricate maze of phenomenological know-how, common lore and other, often historically developed intuitions about what works and what doesn’t. These lectures cover three aspects to help understand LHC results in the Higgs sector and in searches for physics beyond the Standard Model: they discuss the many facets of Higgs physics, which is at the core of this significantly expanded second edition; then QCD, to the degree relevant for LHC measurements; as well as further standard phenomenological background knowledge. They are intended to serve as a brief but sufficiently detailed primer on LHC physics to enable graduate students and all newcomers to the field to find their way through the more advanced literature, and to help those starting to work in this very timely and exciting field of research. Advanced readers will benefit from this course-based text for their own lectures and seminars. .

Author: Ian A. D'Souza
Publisher: World Scientific
ISBN: 9789810210199
Category : Science
Languages : en
Pages : 130

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Book Description
There are a number of unanswered questions which indicate that the Standard Model, successful as it is, cannot be the entire story. One solution to answering these questions is that the Standard Model is an effective low-energy theory of structure hopefully nearby in its energy scale in much the same way that a model of strong interactions among nucleons mediated by pions is an effective theory for the strong interactions of quarks mediated by coloured gluons. This book reviews the Standard Model and then examines the current status of composite models. After developing criteria for judging such models the text discusses two of the major indicators of compositeness, triviality and naturalness. Using this framework as a background the various models are summarized and discussed. This monograph concludes with a chapter describing the constraints imposed on composite models by current measurements of decay rates, magnetic moment measurements, flavour changing processes etc. and describing other ways to look for signatures of compositeness.This monograph attempts to be thorough, covering all aspects of composite models, as found in the literature at the time of completion of the manuscript. As such it should be of interest to any experimental or theoretical physicist having an interest in the subject. The review of the Standard Model in the first chapter is written in such a way that anyone with a basic knowledge of Quantum Field Theory should be able to understand the entire text. As such it could also be used for supplementary reading in graduate courses.

Author: Yi Chen (S.B.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 34

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Book Description
Introduction: The Large Hadron Collider (LHC) located at Geneva, Switzerland, will be the biggest particle accelerator in the world. There are a number of detectors on the LHC ring. The LHCb detector is aimed to study bottom quark physics, which will allow a measurement of the parameters of CP violation in bottom quark productions. The ALICE experiment is specialized in Pb+Pb heavy ion collisions. The ATLAS [3] detector is a general purpose detector, and it will be conducting p+p collision experiments. In addition, the Compact Muon Solenoid (CMS) is currently being commissioned. It will start taking data from as early as late 2008. The detector will be excel in muon detection, but it is also a general purpose detector for p+p and Pb+Pb collsions. The CMS experiment opens up a new window into physics at a unprecedented energy. With the new energy range, a lot of exciting new physics can be examined. The search for the HIGGS boson, which arises from scalar field and is postulated to account for the mass of vector bosons, is one of the main goals of the experiment. The energy range of the LHC is well matched for either confirming its existence or ruling it out. The LHC experiments also want to research on super-symmetry, which potentially explains a lot of open questions for physics beyond the standard model. Although the CMS detector will devote most of its time running proton-proton collisions, one month of each year it will be running lead-lead collisions at center-of-mass energy of 5.5 TeV. Through heavy ion collisions more about the properties of the quark-gluon plasma can be studied, like the viscosity or opacity. In preparation for further studies to the lead-lead collisions, it is interesting to test the basic detector capabilities by studying basic particle reconstruction capabilities. Reconstruction of prompt photon in the heavy ion background has been studied by the MIT heavy ion group last summer, and it leads to the main goal of this thesis. Electrons are one of the main background of the photons, and certainly an important particle type that future studies might need. Inside the CMS detector there will be a roughly constant magnetic field 4.0 Tesla maintained by a superconducting magnet, which allows good measurement of the particle momentum. A slice of the detector is shown in Figure 1. The detector consists of several parts, from inside to outside there are silicon trackers, electromagnetic calorimeter (ECAL), hadronic calorimeter (HCAL), and finally the muon chambers. The tracker is specialized of measuring the momentum of charged particles. The particles will leave a trace on the tracker as they fly through the detector. One important feature about the readout of the tracker is that the output is not binary. Instead, it has an multiple-bit ADC value which allows for better measurement of the direction and better identification of the particle that passes through the tracker. This makes the tracker good for heavy ion events. The electromagnetic and hadronic calorimeters measure energies of different types of particles. Particles such as electrons and photons will deposit most of its energy into the electromagnetic calorimeters, whereas hadrons dump most of their energy into the hadronic calorimeter. The measurement of missing energy in hadronic calorimeter also provides signature of new particles. This study will be focused on the reconstruction of electrons in heavy ion back ground. The reconstructed electrons are then used to show that the reconstruction of the invariant mass of Z0 boson in heavy ion background is possible. The expected number for various particles is listed in section 2. In section 3 the simulated samples used for the study. In the following two sections the reconstruction procedure and the reconstruction properties for electrons. In section 6 the background sources to electrons and the reconstruction of Zo are discussed. Last but not least, additional cuts used for Z0 reconstruction and the results are written in section 7.