New Heavy Bosons (W′, Z′, Leptoquarks, Etc.), Searches
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Search for Second Generation Scalar Leptoquark Pairs with the Atlas Detector
SEARCH FOR SECOND GENERATION SCALAR LEPTOQUARK PAIRS WITH THE ATLAS DETECTOR by Shanti Wendler Master of Science, University of Pittsburgh, 2007 Submitted to the Graduate Faculty of the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2010 UNIVERSITY OF PITTSBURGH PHYSICS DEPARTMENT This dissertation was presented by Shanti Wendler It was defended on July 21st, 2010 and approved by Vittorio Paolone, University of Pittsburgh, Associate Professor, Dept. of Physics Vladimir Savinov, University of Pittsburgh, Associate Professor, Dept. of Physics Adam Leibovich, University of Pittsburgh, Associate Professor, Dept. of Physics Arthur Kosowsky, University of Pittsburgh, Associate Professor, Dept. of Physics Roy Briere, Carnegie Mellon University, Associate Professor, Dept. of Physics Dissertation Director: Vittorio Paolone, University of Pittsburgh, Associate Professor, Dept. of Physics ii SEARCH FOR SECOND GENERATION SCALAR LEPTOQUARK PAIRS WITH THE ATLAS DETECTOR Shanti Wendler, PhD University of Pittsburgh, 2010 Proton collisions at the Large Hadron Collider could provide evidence for the existence of leptoquarks, hypothetical bosons that couple directly to leptons and quarks. Monte Carlo based studies of second generation leptoquark pair production in the ATLAS detector are presented, as well as predictions for discovery and exclusion potential with early ATLAS data. iii TABLE OF CONTENTS 1.0 INTRODUCTION .................................1 2.0 ATLAS DETECTOR AND ITS PERFORMANCE ............2 2.1 Magnet System.................................4 2.2 Inner Detector..................................7 2.2.1 Pixel Detector..............................7 2.2.2 Semiconductor Tracker..........................8 2.2.3 Transition Radiation Tracker......................9 2.2.4 Track Reconstruction in the ID..................... 10 2.2.5 Tracking Performance......................... -
Triple Vector Boson Production at the LHC
Triple Vector Boson Production at the LHC Dan Green Fermilab - CMS Dept. ([email protected]) Introduction The measurement of the interaction among vector bosons is crucial to understanding electroweak symmetry breaking. Indeed, data from LEP-II have already determined triple vector boson couplings and a first measurement of quartic couplings has been made [1]. It is important to explore what additional information can be supplied by future LHC experiments. One technique is to use “tag” jets to identify vector boson fusion processes leading to two vector bosons and two tag jets in the final state. [2] However, the necessity of two quarks simultaneously radiating a W boson means that the cross section is rather small. Another approach is to study the production of three vector bosons in the final state which are produced by the Drell- Yan mechanism. There is a clear tradeoff, in that valence-valence processes are not allowed, which limits the mass range which can be explored using this mechanism, although the cross sections are substantially larger than those for vector boson fusion. Triple Vector Boson Production A Z boson decaying into lepton pairs is required in the final state in order to allow for easy triggering at the LHC and to insure a clean sample of Z plus four jets. Possible final states are ZWW, ZWZ and ZZZ. Assuming that the second and third bosons are reconstructed from their decay into quark pairs, the W and Z will not be easily resolved given the achievable dijet mass resolution. Therefore, the final states of interest contain a Z which decays into leptons and four jets arising for the quark decays of the other two vector bosons. -
Search for Second Generation Leptoquarks with ATLAS at the LHC
Search for Second Generation Leptoquarks with ATLAS at the LHC Dissertation der Fakult¨atf¨urPhysik der Ludwig-Maximilians-Universit¨atM¨unchen vorgelegt von Gernot Krobath geboren in Heidelberg M¨unchen, den 18. Juli 2008 1. Gutachter: Prof. Dr. Dorothee Schaile 2. Gutachter: Prof. Dr. Wolfgang D¨unnweber Tag der m¨undlichen Pr¨ufung: 24.09.2008 Abstract The Large Hadron Collider will collide protons with protons at a center-of-mass energy of up to 14 TeV. New physics phenomena and new particles are pre- dicted to be detectable with the ATLAS detector at the Large Hadron Collider. One of these predicted new particles beyond the Standard Model are leptoquarks. This thesis deals with the search for scalar second generation leptoquarks produced in pairs. Second generation leptoquarks decay into a muon-type lepton and a quark. In this thesis the decay of both second generation leptoquarks into a muon and a quark is considered. Since pair production is studied the final state consists of two high-energetic muons and two high-energetic jets. This thesis studies second generation leptoquarks with masses of mLQ = 300 GeV, mLQ = 400 GeV, mLQ = 600 GeV and mLQ = 800 GeV. The best cut variables for the discrimination between the signal and the main Standard Model backgrounds ∗ t¯t and Z/γ found in this analysis are the pT of the muons, ST (the scalar sum of the transverse momenta of the two selected muons and the transverse energies of the two selected jets), the mass of the selected dimuon system and the recon- structed leptoquark mass. -
Vector Boson Scattering Processes: Status and Prospects
Vector Boson Scattering Processes: Status and Prospects Diogo Buarque Franzosi (ed.)g,d, Michele Gallinaro (ed.)h, Richard Ruiz (ed.)i, Thea K. Aarrestadc, Mauro Chiesao, Antonio Costantinik, Ansgar Dennert, Stefan Dittmaierf, Flavia Cetorellil, Robert Frankent, Pietro Govonil, Tao Hanp, Ashutosh V. Kotwala, Jinmian Lir, Kristin Lohwasserq, Kenneth Longc, Yang Map, Luca Mantanik, Matteo Marchegianie, Mathieu Pellenf, Giovanni Pellicciolit, Karolos Potamianosn,Jurgen¨ Reuterb, Timo Schmidtt, Christopher Schwanm, Michał Szlepers, Rob Verheyenj, Keping Xiep, Rao Zhangr aDepartment of Physics, Duke University, Durham, NC 27708, USA bDeutsches Elektronen-Synchrotron (DESY) Theory Group, Notkestr. 85, D-22607 Hamburg, Germany cEuropean Organization for Nuclear Research (CERN) CH-1211 Geneva 23, Switzerland dDepartment of Physics, Chalmers University of Technology, Fysikgården 1, 41296 G¨oteborg, Sweden eSwiss Federal Institute of Technology (ETH) Z¨urich, Otto-Stern-Weg 5, 8093 Z¨urich, Switzerland fUniversit¨atFreiburg, Physikalisches Institut, Hermann-Herder-Straße 3, 79104 Freiburg, Germany gPhysics Department, University of Gothenburg, 41296 G¨oteborg, Sweden hLaborat´oriode Instrumenta¸c˜aoe F´ısicaExperimental de Part´ıculas(LIP), Lisbon, Av. Prof. Gama Pinto, 2 - 1649-003, Lisboa, Portugal iInstitute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego, Cracow 31-342, Poland jUniversity College London, Gower St, Bloomsbury, London WC1E 6BT, United Kingdom kCentre for Cosmology, Particle Physics and Phenomenology (CP3), Universit´eCatholique de Louvain, Chemin du Cyclotron, B-1348 Louvain la Neuve, Belgium lMilano - Bicocca University and INFN, Piazza della Scienza 3, Milano, Italy mTif Lab, Dipartimento di Fisica, Universit`adi Milano and INFN, Sezione di Milano, Via Celoria 16, 20133 Milano, Italy nDepartment of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK oDipartimento di Fisica, Universit`adi Pavia, Via A. -
Basic Ideas of the Standard Model
BASIC IDEAS OF THE STANDARD MODEL V.I. ZAKHAROV Randall Laboratory of Physics University of Michigan, Ann Arbor, Michigan 48109, USA Abstract This is a series of four lectures on the Standard Model. The role of conserved currents is emphasized. Both degeneracy of states and the Goldstone mode are discussed as realization of current conservation. Remarks on strongly interact- ing Higgs fields are included. No originality is intended and no references are given for this reason. These lectures can serve only as a material supplemental to standard textbooks. PRELIMINARIES Standard Model (SM) of electroweak interactions describes, as is well known, a huge amount of exper- imental data. Comparison with experiment is not, however, the aspect of the SM which is emphasized in present lectures. Rather we treat SM as a field theory and concentrate on basic ideas underlying this field theory. Th Standard Model describes interactions of fields of various spins and includes spin-1, spin-1/2 and spin-0 particles. Spin-1 particles are observed as gauge bosons of electroweak interactions. Spin- 1/2 particles are represented by quarks and leptons. And spin-0, or Higgs particles have not yet been observed although, as we shall discuss later, we can say that scalar particles are in fact longitudinal components of the vector bosons. Interaction of the vector bosons can be consistently described only if it is highly symmetrical, or universal. Moreover, from experiment we know that the corresponding couplings are weak and can be treated perturbatively. Interaction of spin-1/2 and spin-0 particles are fixed by theory to a much lesser degree and bring in many parameters of the SM. -
Three Lectures on Meson Mixing and CKM Phenomenology
Three Lectures on Meson Mixing and CKM phenomenology Ulrich Nierste Institut f¨ur Theoretische Teilchenphysik Universit¨at Karlsruhe Karlsruhe Institute of Technology, D-76128 Karlsruhe, Germany I give an introduction to the theory of meson-antimeson mixing, aiming at students who plan to work at a flavour physics experiment or intend to do associated theoretical studies. I derive the formulae for the time evolution of a neutral meson system and show how the mass and width differences among the neutral meson eigenstates and the CP phase in mixing are calculated in the Standard Model. Special emphasis is laid on CP violation, which is covered in detail for K−K mixing, Bd−Bd mixing and Bs−Bs mixing. I explain the constraints on the apex (ρ, η) of the unitarity triangle implied by ǫK ,∆MBd ,∆MBd /∆MBs and various mixing-induced CP asymmetries such as aCP(Bd → J/ψKshort)(t). The impact of a future measurement of CP violation in flavour-specific Bd decays is also shown. 1 First lecture: A big-brush picture 1.1 Mesons, quarks and box diagrams The neutral K, D, Bd and Bs mesons are the only hadrons which mix with their antiparticles. These meson states are flavour eigenstates and the corresponding antimesons K, D, Bd and Bs have opposite flavour quantum numbers: K sd, D cu, B bd, B bs, ∼ ∼ d ∼ s ∼ K sd, D cu, B bd, B bs, (1) ∼ ∼ d ∼ s ∼ Here for example “Bs bs” means that the Bs meson has the same flavour quantum numbers as the quark pair (b,s), i.e.∼ the beauty and strangeness quantum numbers are B = 1 and S = 1, respectively. -
RDًأق Motivated S1 Leptoquark Scenarios
PHYSICAL REVIEW D 99, 055028 (2019) RDðÞ motivated S1 leptoquark scenarios: Impact of interference on the exclusion limits from LHC data Tanumoy Mandal* Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India and Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden † ‡ Subhadip Mitra and Swapnil Raz Center for Computational Natural Sciences and Bioinformatics, International Institute of Information Technology, Hyderabad 500 032, India (Received 28 December 2018; published 21 March 2019) Motivated by the persistent anomalies in the semileptonic B-meson decays, we investigate the −1 3 competency of LHC data to constrain the RDðÞ -favored parameter space in a charge = scalar S leptoquark ( 1) model. We consider some scenarios with one large free coupling to accommodate the RDðÞ anomalies. As a result, some of them dominantly yield nonresonant ττ and τν events at the LHC through the t-channel S1 exchange. So far, no experiment has searched for leptoquarks using these signatures and the relevant resonant leptoquark searches are yet to put any strong exclusion limit on the parameter space. We recast the latest ττ and τν resonance search data to obtain new exclusion limits. The nonresonant processes strongly interfere (destructively in our case) with the Standard Model background and play the determining role in setting the exclusion limits. To obtain precise limits, we include non-negligible effects coming from the subdominant (resonant) pair and inclusive single leptoquark productions systematically in our analysis. To deal with large destructive interference, we make use of the transverse mass distributions from the experiments in our statistical analysis. -
Phenomenology Lecture 6: Higgs
Phenomenology Lecture 6: Higgs Daniel Maître IPPP, Durham Phenomenology - Daniel Maître The Higgs Mechanism ● Very schematic, you have seen/will see it in SM lectures ● The SM contains spin-1 gauge bosons and spin- 1/2 fermions. ● Massless fields ensure: – gauge invariance under SU(2)L × U(1)Y – renormalisability ● We could introduce mass terms “by hand” but this violates gauge invariance ● We add a complex doublet under SU(2) L Phenomenology - Daniel Maître Higgs Mechanism ● Couple it to the SM ● Add terms allowed by symmetry → potential ● We get a potential with infinitely many minima. ● If we expend around one of them we get – Vev which will give the mass to the fermions and massive gauge bosons – One radial and 3 circular modes – Circular modes become the longitudinal modes of the gauge bosons Phenomenology - Daniel Maître Higgs Mechanism ● From the new terms in the Lagrangian we get ● There are fixed relations between the mass and couplings to the Higgs scalar (the one component of it surviving) Phenomenology - Daniel Maître What if there is no Higgs boson? ● Consider W+W− → W+W− scattering. ● In the high energy limit ● So that we have Phenomenology - Daniel Maître Higgs mechanism ● This violate unitarity, so we need to do something ● If we add a scalar particle with coupling λ to the W ● We get a contribution ● Cancels the bad high energy behaviour if , i.e. the Higgs coupling. ● Repeat the argument for the Z boson and the fermions. Phenomenology - Daniel Maître Higgs mechanism ● Even if there was no Higgs boson we are forced to introduce a scalar interaction that couples to all particles proportional to their mass. -
Introduction to Supersymmetry
Introduction to Supersymmetry Pre-SUSY Summer School Corpus Christi, Texas May 15-18, 2019 Stephen P. Martin Northern Illinois University [email protected] 1 Topics: Why: Motivation for supersymmetry (SUSY) • What: SUSY Lagrangians, SUSY breaking and the Minimal • Supersymmetric Standard Model, superpartner decays Who: Sorry, not covered. • For some more details and a slightly better attempt at proper referencing: A supersymmetry primer, hep-ph/9709356, version 7, January 2016 • TASI 2011 lectures notes: two-component fermion notation and • supersymmetry, arXiv:1205.4076. If you find corrections, please do let me know! 2 Lecture 1: Motivation and Introduction to Supersymmetry Motivation: The Hierarchy Problem • Supermultiplets • Particle content of the Minimal Supersymmetric Standard Model • (MSSM) Need for “soft” breaking of supersymmetry • The Wess-Zumino Model • 3 People have cited many reasons why extensions of the Standard Model might involve supersymmetry (SUSY). Some of them are: A possible cold dark matter particle • A light Higgs boson, M = 125 GeV • h Unification of gauge couplings • Mathematical elegance, beauty • ⋆ “What does that even mean? No such thing!” – Some modern pundits ⋆ “We beg to differ.” – Einstein, Dirac, . However, for me, the single compelling reason is: The Hierarchy Problem • 4 An analogy: Coulomb self-energy correction to the electron’s mass A point-like electron would have an infinite classical electrostatic energy. Instead, suppose the electron is a solid sphere of uniform charge density and radius R. An undergraduate problem gives: 3e2 ∆ECoulomb = 20πǫ0R 2 Interpreting this as a correction ∆me = ∆ECoulomb/c to the electron mass: 15 0.86 10− meters m = m + (1 MeV/c2) × . -
116. Leptoquarks 1 116
116. Leptoquarks 1 116. Leptoquarks Updated August 2019 by S. Rolli (US Department of Energy) and M. Tanabashi (Nagoya U.) Leptoquarks are hypothetical particles carrying both baryon number (B) and lepton number (L). The possible quantum numbers of leptoquark states can be restricted by assuming that their direct interactions with the ordinary standard model (SM) fermions are dimensionless and invariant under the SM gauge group. Table 116.1 shows the list of all possible quantum numbers with this assumption [1]. The columns of SU(3)C, SU(2)W , and U(1)Y in Table 116.1 indicate the QCD representation, the weak isospin representation, and the weak hypercharge, respectively. The spin of a leptoquark state is taken to be 1 (vector leptoquark) or 0 (scalar leptoquark). Table 116.1: Possible leptoquarks and their quantum numbers. Spin 3B + L SU(3)c SU(2)W U(1)Y Allowed coupling 0 2 3¯ 1 1/3q ¯c ℓ oru ¯c e − L L R R 0 2 3¯ 1 4/3 d¯c e − R R 0 2 3¯ 3 1/3q ¯c ℓ − L L 1 2 3¯ 2 5/6q ¯c γµe or d¯c γµℓ − L R R L 1 2 3¯ 2 1/6u ¯c γµℓ − − R L 0 03 2 7/6q ¯LeR oru ¯RℓL 0 03 2 1/6 d¯RℓL µ µ 1 03 1 2/3q ¯Lγ ℓL or d¯Rγ eR µ 1 03 1 5/3u ¯Rγ eR µ 1 03 3 2/3q ¯Lγ ℓL If we do not require leptoquark states to couple directly with SM fermions, different assignments of quantum numbers become possible [2,3]. -
Search for Non Standard Model Higgs Boson
Thirteenth Conference on the Intersections of Particle and Nuclear Physics May 29 – June 3, 2018 Palm Springs, CA Search for Non Standard Model Higgs Boson Ana Elena Dumitriu (IFIN-HH, CPPM), On behalf of the ATLAS Collaboration 5/18/18 1 Introduction and Motivation ● The discovery of the Higgs (125 GeV) by ATLAS and CMS collaborations → great success of particle physics and especially Standard Model (SM) ● However.... – MORE ROOM Hierarchy problem FOR HIGGS PHYSICS – Origin of dark matter, dark energy BEYOND SM – Baryon Asymmetry – Gravity – Higgs br to Beyond Standard Model (BSM) particles of BRBSM < 32% at 95% C.L. ● !!!!!!There is plenty of room for Higgs physics beyond the Standard Model. ● There are several theoretical models with an extended Higgs sector. – 2 Higgs Doublet Models (2HDM). Having two complex scalar SU(2) doublets, they are an effective extension of the SM. In total, 5 different Higgs bosons are predicted: two CP even and one CP odd electrically neutral Higgs bosons, denoted by h, H, and A, respectively, and two charged Higgs bosons, H±. The parameters used to describe a 2HDM are the Higgs boson masses and the ratios of their vacuum expectation values. ● type I, where one SU(2) doublet gives masses to all leptons and quarks and the other doublet essentially decouples from fermions ● type II, where one doublet gives mass to up-like quarks (and potentially neutrinos) and the down-type quarks and leptons receive mass from the other doublet. – Supersymmetry (SUSY), which brings along super-partners of the SM particles. The Minimal Supersymmetric Standard Model (MSSM), whose Higgs sector is equivalent to the one of a constrained 2HDM of type II and the next-to MSSM (NMSSM) are among the experimentally best tested models, because they provide good benchmarks for SUSY. -
JHEP05(2010)010 , 6 − Ing Springer and 10 May 4, 2010 9 : April 19, 2010 − : Tic Inflationary December 3, 2009 : Published Lar Potential, and No S
Published for SISSA by Springer Received: December 3, 2009 Accepted: April 19, 2010 Published: May 4, 2010 Light inflaton hunter’s guide JHEP05(2010)010 F. Bezrukova and D. Gorbunovb aMax-Planck-Institut f¨ur Kernphysik, P.O. Box 103980, 69029 Heidelberg, Germany bInstitute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary prospect 7a, Moscow 117312, Russia E-mail: [email protected], [email protected] Abstract: We study the phenomenology of a realistic version of the chaotic inflationary model, which can be fully and directly explored in particle physics experiments. The inflaton mixes with the Standard Model Higgs boson via the scalar potential, and no additional scales above the electroweak scale are present in the model. The inflaton-to- Higgs coupling is responsible for both reheating in the Early Universe and the inflaton production in particle collisions. We find the allowed range of the light inflaton mass, 270 MeV . mχ . 1.8 GeV, and discuss the ways to find the inflaton. The most promising are two-body kaon and B-meson decays with branching ratios of orders 10−9 and 10−6, respectively. The inflaton is unstable with the lifetime 10−9–10−10 s. The inflaton decays can be searched for in a beam-target experiment, where, depending on the inflaton mass, from several billions to several tenths of millions inflatons can be produced per year with modern high-intensity beams. Keywords: Cosmology of Theories beyond the SM, Rare Decays ArXiv ePrint: 0912.0390 Open Access doi:10.1007/JHEP05(2010)010 Contents 1 Introduction 1 2 The model 3 3 Inflaton decay palette 6 4 Inflaton from hadron decays 10 JHEP05(2010)010 5 Inflaton production in particle collisions 12 6 Limits from direct searches and predictions for forthcoming experiments 14 7 Conclusions 16 A The νMSM extension 16 1 Introduction In this paper we present an example of how (low energy) particle physics experiments can directly probe the inflaton sector (whose dynamics is important at high energies in the very Early Universe).