DOCSLIB.ORG

Fabrizio Trovato

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Fabrizio Trovato High energy Physics on Search for chargino and neutralino Fabrizio Trovato production with three leptons and missing July 10th-17th 2019 - Ghent, Belgium transverse momentum in the final states at √s = 13 TeV European Physics society Conference bstract with the ATLAS detector ± 0 Searches are presented for the direct production of a chargino and a neutralino, pp → χ˜1 χ˜2 , where the chargino decays to A ± 0 ± ± the lightest neutralino and the W boson, χ˜1 → χ˜1 (W → ℓ ν), while the neutralino decays to the lightest neutralino and χ 0 χ 0 χ 0 χ 0 either the Z boson ˜2 → ˜1 (Z → ℓℓ) or the 125 GeV Higgs boson, ˜2 → ˜1 (h → ℓℓ). The final states considered for the search The ATLAS detector have large missing transverse momentum and three isolated light leptons (electrons and muons). The analyses are based on 36.1 fb-1 of √s = 13 TeV proton-proton collision data delivered by the Large Hadron Collider (LHC) and recorded with the ATLAS detector. Physics scenario • Supersymmetry (SUSY) is a principle that predicts a fermion-boson symmetry [1] (Figure 1); • SUSY doubles particle content compared to Standard Model (SM). Many free parameters (masses, couplings); • The electroweakinos are eigenstates of the SUSY partners of charged SM bosons (charginos) and neutral SM bosons (neutralinos). Why is Electroweak SUSY interesting? Analysis strategy Signal Regions (SRs) Figure 1. Particle content of the Minimal Supersymmetric Standand Model (MSSM). Cut-and-count optimisation of cuts that permit a good Chargino/neutralino via WZ and Wh signal/background discrimination Control Regions (CRs) √s = 13 TeV. Irreducible Fake or non-prompt (FNP) backgrounds normalised to Estimation of reducible data in dedicated background with dedicated data-driven techniques production becomes becomes production background-enriched regions If squarks and gluinos gluinos and squarks If then electroweak SUSY SUSY then electroweak dominant at at dominant heavier than electroweakinos, electroweakinos, than heavier Validation Regions (VRs) Data/MC comparison in Mostly WW, ττ, ZZ Figure 2. Typical SUSY cross sections at the nominal Run2 centre of mass energy of the LHC, taken from regions close to SRs https://twiki.cern.ch/twiki/bin/view/LHCPhysics/SUSYCrossSections. χ˜ 0 • R-parity-conserving model: 1 R-parity Signal region definitions stable (Dark Matter candidate); 3(B L)+2s PR =( 1) − • A Same Flavour Same Sign (SFSS) lepton • Considered final state: three − • At least one Same Flavour Opposite Sign ± W ℓ ± pair and an additional DifferentF lavour W ℓ electrons or muons and missing transverse momentum; (SFOS) lepton pair; ΔΦSS -1 Opposite Sign (DFOS) lepton; • TheWh and WZ analyses have been explored with 36.1 fb • Binned in jet multiplicity, missing ΔR OS,near ± Z/h ℓ ± • Binning approach in jet multiplicity, using h ℓ' dataset collected with the ATLAS detector [3][4]. transverse energy and transverse mass. ( ) ℓ ± ℓ ' topological variables. Irreducible background estimation In both analyses, W+Z background is normalised to data, using two different control regions. For example, in the Wh analysis, events in a 20-GeV window around the Z boson miss mass and with ET > 80 GeV were selected. Table 1. Signal regions used in the SFOS flavour/sign selection, targeting WZ model. Table 3. Signal regions used in the SFSS+DFOS flavour/sign selection, targeting Wh model. Conclusion and outlook Table 2. Signal regions used in the SFOS flavour/sign selection, targeting Wh model. Results Figure 7. Data/MC comparison in the W+Z CR and VRs used in the multileptonic searches for Wh. FNP background estimation Data-driven techniques are used to estimate the FNP in the SRs. In the WZ analysis, the Fake Factor method [5] correlates the number of FNP leptons to the number of leptons that pass specific Figure 9. Data/MC comparisons for some of the WZ and Wh analyses SRs (left and right, respectively). Figure 9. Summary plot for chargino/neutralino searches with the ATLAS detector. Wh SFSS+DFOS region exploits the invariant mass of the leptons used in the definition of the ΔR . “loose” (antiID) or “tight” OS,near -1 (ID) selections. • The analyses with the full Run2 139 fb will target the same The method is validated in class of simplified models, addressing WZ and Wh searches VRs (Figure 8). simultaneously: • Similar backgrounds and challenges. • Chargino/neutralino searches with boson-mediated decays NID F = Figure 8. Data/MC agreement in a jet multiplicity to multileptonic final states will remain one of the key NantiID inclusive W+Z VR for the WZ analysis. analyses to search for SUSY in the long term, also in view of FNP MC prompt future luminosity upgrades of the LHC. NT = F (NL NL ) Figure 10. 1D limit at 95% of C.L. for the Wh analysis when the mass splitting is equal to 130 GeV − (kinematic limit for on-shell Higgs boson) (left). Limits at 95% of C.L. for the WZ analysis (right). [1] S. P. Martin, A Supersymmetry primer, (1997), [Adv. Ser. Direct. High Energy Phys.18,1(1998)]. Author: [email protected] [2] ATLAS Collaboration, The ATLAS Experiment at the CERN Large Hadron Collider, JINST 3 (2008) S08003. [3] ATLAS Collaboration, Search for electroweak production of supersymmetric particles in the two and three lepton final state at √s = 13 TeV with the ATLAS detector, Eur. Phys. J. C 78 (2018) 995. https://doi.org/10.1140/epjc/s10052-018-6423-7. [4] ATLAS Collaboration, Search for chargino and neutralino production in final states with a Higgs boson and missing transverse momentum at √s = 13 TeV with the ATLAS detector. arXiv:1812.09432 [hep-ex] (accepted by PRD). [5] ATLAS Collaboration, Measurement of the W±Z boson pair-production cross section in pp collisions at √s = 13 TeV with the ATLAS Detector, Phys. Lett. B 762 (2016) 1. arXiv: 1606.04017 [hep-ex]..
Load more

Recommended publications
  • Constraints from Electric Dipole Moments on Chargino Baryogenesis in the Minimal Supersymmetric Standard Model
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by National Tsing Hua University Institutional Repository PHYSICAL REVIEW D 66, 116008 ͑2002͒ Constraints from electric dipole moments on chargino baryogenesis in the minimal supersymmetric standard model Darwin Chang NCTS and Physics Department, National Tsing-Hua University, Hsinchu 30043, Taiwan, Republic of China and Theory Group, Lawrence Berkeley Lab, Berkeley, California 94720 We-Fu Chang NCTS and Physics Department, National Tsing-Hua University, Hsinchu 30043, Taiwan, Republic of China and TRIUMF Theory Group, Vancouver, British Columbia, Canada V6T 2A3 Wai-Yee Keung NCTS and Physics Department, National Tsing-Hua University, Hsinchu 30043, Taiwan, Republic of China and Physics Department, University of Illinois at Chicago, Chicago, Illinois 60607-7059 ͑Received 9 May 2002; revised 13 September 2002; published 27 December 2002͒ A commonly accepted mechanism of generating baryon asymmetry in the minimal supersymmetric standard model ͑MSSM͒ depends on the CP violating relative phase between the gaugino mass and the Higgsino ␮ term. The direct constraint on this phase comes from the limit of electric dipole moments ͑EDM’s͒ of various light fermions. To avoid such a constraint, a scheme which assumes that the first two generation sfermions are very heavy is usually evoked to suppress the one-loop EDM contributions. We point out that under such a scheme the most severe constraint may come from a new contribution to the electric dipole moment of the electron, the neutron, or atoms via the chargino sector at the two-loop level. As a result, the allowed parameter space for baryogenesis in the MSSM is severely constrained, independent of the masses of the first two generation sfermions.
    [Show full text]
  • Table of Contents (Print)
    PERIODICALS PHYSICAL REVIEW D Postmaster send address changes to: For editorial and subscription correspondence, PHYSICAL REVIEW D please see inside front cover APS Subscription Services „ISSN: 0556-2821… Suite 1NO1 2 Huntington Quadrangle Melville, NY 11747-4502 THIRD SERIES, VOLUME 69, NUMBER 7 CONTENTS D1 APRIL 2004 RAPID COMMUNICATIONS ϩ 0 ⌼ ϩ→ ␺ ϩ 0→ ␺ 0 Measurement of the B /B production ratio from the (4S) meson using B J/ K and B J/ KS decays (7 pages) ............................................................................ 071101͑R͒ B. Aubert et al. ͑BABAR Collaboration͒ Cabibbo-suppressed decays of Dϩ→␲ϩ␲0,KϩK¯ 0,Kϩ␲0 (5 pages) .................................. 071102͑R͒ K. Arms et al. ͑CLEO Collaboration͒ Ϯ→␹ Ϯ ͑ ͒ Measurement of the branching fraction for B c0K (7 pages) ................................... 071103R B. Aubert et al. ͑BABAR Collaboration͒ Generalized Ward identity and gauge invariance of the color-superconducting gap (5 pages) .............. 071501͑R͒ De-fu Hou, Qun Wang, and Dirk H. Rischke ARTICLES Measurements of ␺(2S) decays into vector-tensor final states (6 pages) ............................... 072001 J. Z. Bai et al. ͑BES Collaboration͒ Measurement of inclusive momentum spectra and multiplicity distributions of charged particles at ͱsϳ2 –5 GeV (7 pages) ................................................................... 072002 J. Z. Bai et al. ͑BES Collaboration͒ Production of ␲ϩ, ␲Ϫ, Kϩ, KϪ, p, and ¯p in light ͑uds͒, c, and b jets from Z0 decays (26 pages) ........ 072003 Koya Abe et al. ͑SLD Collaboration͒ Heavy flavor properties of jets produced in pp¯ interactions at ͱsϭ1.8 TeV (21 pages) .................. 072004 D. Acosta et al. ͑CDF Collaboration͒ Electric charge and magnetic moment of a massive neutrino (21 pages) ............................... 073001 Maxim Dvornikov and Alexander Studenikin ␶→␲␲␲␯␶ decays in the resonance effective theory (13 pages) ....................................
    [Show full text]
  • Study of $ S\To D\Nu\Bar {\Nu} $ Rare Hyperon Decays Within the Standard
    Study of s dνν¯ rare hyperon decays in the Standard Model and new physics → Xiao-Hui Hu1 ∗, Zhen-Xing Zhao1 † 1 INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, MOE Key Laboratory for Particle Physics, Astrophysics and Cosmology, School of Physics and Astronomy, Shanghai Jiao-Tong University, Shanghai 200240, P.R. China FCNC processes offer important tools to test the Standard Model (SM), and to search for possible new physics. In this work, we investigate the s → dνν¯ rare hyperon decays in SM and beyond. We 14 11 find that in SM the branching ratios for these rare hyperon decays range from 10− to 10− . When all the errors in the form factors are included, we find that the final branching fractions for most decay modes have an uncertainty of about 5% to 10%. After taking into account the contribution from new physics, the generalized SUSY extension of SM and the minimal 331 model, the decay widths for these channels can be enhanced by a factor of 2 ∼ 7. I. INTRODUCTION The flavor changing neutral current (FCNC) transitions provide a critical test of the Cabibbo-Kobayashi-Maskawa (CKM) mechanism in the Standard Model (SM), and allow to search for the possible new physics. In SM, FCNC transition s dνν¯ proceeds through Z-penguin and electroweak box diagrams, and thus the decay probablitities are strongly→ suppressed. In this case, a precise study allows to perform very stringent tests of SM and ensures large sensitivity to potential new degrees of freedom. + + 0 A large number of studies have been performed of the K π νν¯ and KL π νν¯ processes, and reviews of these two decays can be found in [1–6].
    [Show full text]
  • Thesissubmittedtothe Florida State University Department of Physics in Partial Fulfillment of the Requirements for Graduation with Honors in the Major
    Florida State University Libraries 2016 Search for Electroweak Production of Supersymmetric Particles with two photons, an electron, and missing transverse energy Paul Myles Eugenio Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] ASEARCHFORELECTROWEAK PRODUCTION OF SUPERSYMMETRIC PARTICLES WITH TWO PHOTONS, AN ELECTRON, AND MISSING TRANSVERSE ENERGY Paul Eugenio Athesissubmittedtothe Florida State University Department of Physics in partial fulfillment of the requirements for graduation with Honors in the Major Spring 2016 2 Abstract A search for Supersymmetry (SUSY) using a final state consisting of two pho- tons, an electron, and missing transverse energy. This analysis uses data collected by the Compact Muon Solenoid (CMS) detector from proton-proton collisions at a center of mass energy √s =13 TeV. The data correspond to an integrated luminosity of 2.26 fb−1. This search focuses on a R-parity conserving model of Supersymmetry where electroweak decay of SUSY particles results in the lightest supersymmetric particle, two high energy photons, and an electron. The light- est supersymmetric particle would escape the detector, thus resulting in missing transverse energy. No excess of missing energy is observed in the signal region of MET>100 GeV. A limit is set on the SUSY electroweak Chargino-Neutralino production cross section. 3 Contents 1 Introduction 9 1.1 Weakly Interacting Massive Particles . ..... 10 1.2 SUSY ..................................... 12 2 CMS Detector 15 3Data 17 3.1 ParticleFlowandReconstruction . .. 17 3.1.1 ECALClusteringandR9. 17 3.1.2 Conversion Safe Electron Veto . 18 3.1.3 Shower Shape . 19 3.1.4 Isolation .
    [Show full text]
  • Jhep11(2016)148
    Published for SISSA by Springer Received: August 9, 2016 Revised: October 28, 2016 Accepted: November 20, 2016 Published: November 24, 2016 JHEP11(2016)148 Split NMSSM with electroweak baryogenesis S.V. Demidov,a;b D.S. Gorbunova;b and D.V. Kirpichnikova aInstitute for Nuclear Research of the Russian Academy of Sciences, 60th October Anniversary prospect 7a, Moscow 117312, Russia bMoscow Institute of Physics and Technology, Institutsky per. 9, Dolgoprudny 141700, Russia E-mail: [email protected], [email protected], [email protected] Abstract: In light of the Higgs boson discovery and other results of the LHC we re- consider generation of the baryon asymmetry in the split Supersymmetry model with an additional singlet superfield in the Higgs sector (non-minimal split SUSY). We find that successful baryogenesis during the first order electroweak phase transition is possible within a phenomenologically viable part of the model parameter space. We discuss several phenomenological consequences of this scenario, namely, predictions for the electric dipole moments of electron and neutron and collider signatures of light charginos and neutralinos. Keywords: Supersymmetry Phenomenology ArXiv ePrint: 1608.01985 Open Access, c The Authors. doi:10.1007/JHEP11(2016)148 Article funded by SCOAP3. Contents 1 Introduction1 2 Non-minimal split supersymmetry3 3 Predictions for the Higgs boson mass5 4 Strong first order EWPT8 JHEP11(2016)148 5 Baryon asymmetry9 6 EDM constraints and light chargino phenomenology 12 7 Conclusion 13 A One loop corrections to Higgs mass in split NMSSM 14 A.1 Tree level potential of scalar sector in the broken phase 14 A.2 Chargino-neutralino sector of split NMSSM 16 A.3 One-loop correction to Yukawa coupling of top quark 17 1 Introduction Any phenomenologically viable particle physics model should explain the observed asym- metry between matter and antimatter in the Universe.
    [Show full text]
  • Mass Degeneracy of the Higgsinos
    CERN–TH/95–337 Mass Degeneracy of the Higgsinos Gian F. Giudice1 and Alex Pomarol Theory Division, CERN CH-1211 Geneva 23, Switzerland Abstract The search for charginos and neutralinos at LEP2 can become problematic if these particles are almost mass degenerate with the lightest neutralino. Unfortunately this is the case in the region where these particles are higgsino-like. We show that, in this region, radiative corrections to the higgsino mass splittings can be as large as the tree-level values, if the mixing between the two stop states is large. We also show that the degree of degeneracy of the higgsinos substantially increases if a large phase is present in the higgsino mass term µ. CERN–TH/95–337 December 1995 1On leave of absence from INFN Sezione di Padova, Padua, Italy. The search for charginos (˜χ+) at LEP2 is one of the most promising ways of discovering low-energy supersymmetry. If theχ ˜+ decays into the lightest neutralino (˜χ0) and a virtual W +, it can be discovered at LEP2 (with a L = 500 pb−1) whenever its production cross R section is larger than about 0.1–0.3pbandmχ˜0 is within the range mχ˜0 ∼> 20 GeV and mχ˜+ − mχ˜0 ∼> 5–10 GeV [1]. Therefore, the chargino can be discovered almost up to the LEP2 kinematical limit, unless one of the following three conditions occurs: i) The sneutrino (˜ν) is light and the chargino is mainly gaugino-like. In this case theν ˜ t-channel exchange interferes destructively with the gauge-boson exchange and can reduce the chargino production cross section below the minimum values required for observability, 0.1–0.3 pb.
    [Show full text]
  • Table of Contents (Print)
    PERIODICALS PHYSICAL REVIEW D Postmaster send address changes to: For editorial and subscription correspondence, American Institute of Physics please see inside front cover 500 Sunnyside Boulevard (ISSN: 0556-2821) Woodbury, NY 11797-2999 THIRD SERIES, VOLUME 55, NUMBER 3 CONTENTS 1 FEBRUARY 1997 RAPID COMMUNICATIONS Search for f mesons in t lepton decay ............................................................. R1119 P. Avery et al. ~CLEO Collaboration! Is factorization for isolated photon cross sections broken? .............................................. R1124 P. Aurenche, M. Fontannaz, J. Ph. Guillet, A. Kotikov, and E. Pilon Long distance contribution to D pl1l2 ........................................................... R1127 Paul Singer and Da-Xin Zhang→ Forward scattering amplitude of virtual longitudinal photons at zero energy ............................... R1130 B. L. Ioffe Improving flavor symmetry in the Kogut-Susskind hadron spectrum ...................................... R1133 Tom Blum, Carleton DeTar, Steven Gottlieb, Kari Rummukainen, Urs M. Heller, James E. Hetrick, Doug Toussaint, R. L. Sugar, and Matthew Wingate Anomalous U~1!-mediated supersymmetry breaking, fermion masses, and natural suppression of FCNC and CP-violating effects ............................................................................. R1138 R. N. Mohapatra and Antonio Riotto ARTICLES 0 Observation of L b J/c L at the Fermilab proton-antiproton collider .................................... 1142 F. Abe et al.→~CDF Collaboration! Measurement of the branching ratios c8 e1e2, c8 J/cpp, and c8 J/ch ............................ 1153 T. A. Armstrong et al. ~Fermilab→ E760 Collaboration→ ! → Measurement of the differences in the total cross section for antiparallel and parallel longitudinal spins and a measurement of parity nonconservation with incident polarized protons and antiprotons at 200 GeV/c .......... 1159 D. P. Grosnick et al. ~E581/704 Collaboration! Statistical properties of the linear s model used in dynamical simulations of DCC formation ................
    [Show full text]
  • Supersymmetric Particle Searches
    Citation: K.A. Olive et al. (Particle Data Group), Chin. Phys. C38, 090001 (2014) (URL: http://pdg.lbl.gov) Supersymmetric Particle Searches A REVIEW GOES HERE – Check our WWW List of Reviews A REVIEW GOES HERE – Check our WWW List of Reviews SUPERSYMMETRIC MODEL ASSUMPTIONS The exclusion of particle masses within a mass range (m1, m2) will be denoted with the notation “none m m ” in the VALUE column of the 1− 2 following Listings. The latest unpublished results are described in the “Supersymmetry: Experiment” review. A REVIEW GOES HERE – Check our WWW List of Reviews CONTENTS: χ0 (Lightest Neutralino) Mass Limit 1 e Accelerator limits for stable χ0 − 1 Bounds on χ0 from dark mattere searches − 1 χ0-p elastice cross section − 1 eSpin-dependent interactions Spin-independent interactions Other bounds on χ0 from astrophysics and cosmology − 1 Unstable χ0 (Lighteste Neutralino) Mass Limit − 1 χ0, χ0, χ0 (Neutralinos)e Mass Limits 2 3 4 χe ,eχ e(Charginos) Mass Limits 1± 2± Long-livede e χ± (Chargino) Mass Limits ν (Sneutrino)e Mass Limit Chargede Sleptons e (Selectron) Mass Limit − µ (Smuon) Mass Limit − e τ (Stau) Mass Limit − e Degenerate Charged Sleptons − e ℓ (Slepton) Mass Limit − q (Squark)e Mass Limit Long-livede q (Squark) Mass Limit b (Sbottom)e Mass Limit te (Stop) Mass Limit eHeavy g (Gluino) Mass Limit Long-lived/lighte g (Gluino) Mass Limit Light G (Gravitino)e Mass Limits from Collider Experiments Supersymmetrye Miscellaneous Results HTTP://PDG.LBL.GOV Page1 Created: 8/21/2014 12:57 Citation: K.A. Olive et al.
    [Show full text]
  • 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) × .
    [Show full text]
  • Study of the Rare Hyperon Decays in the Standard Model and New Physics*
    Chinese Physics C Vol. 43, No. 9 (2019) 093104 Study of the s ! dνν¯ rare hyperon decays in the Standard Model and new physics* 1) 2) Xiao-Hui Hu(胡晓会) Zhen-Xing Zhao(赵振兴) INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, MOE Key Laboratory for Particle Physics, Astrophysics and Cosmology, School of Physics and Astronomy, Shanghai Jiao-Tong University, Shanghai 200240, China Abstract: FCNC processes offer important tools to test the Standard Model (SM) and to search for possible new physics. In this work, we investigate the s ! dνν¯ rare hyperon decays in SM and beyond. We find that in SM the branching ratios for these rare hyperon decays range from 10−14 to 10−11 . When all the errors in the form factors are included, we find that the final branching ratios for most decay modes have an uncertainty of about 5% to 10%. After taking into account the contribution from new physics, the generalized SUSY extension of SM and the minimal 331 model, the decay widths for these channels can be enhanced by a factor of 2 ∼ 7. Keywords: branching ratios, rare hyperon decays, form factors, light-front approach, new physics PACS: 12.39.-x, 12.60.-i DOI: 10.1088/1674-1137/43/9/093104 1 Introduction flight technique, and the corresponding observed upper limit is [8] : B + ! π+νν < × −10; : The flavor changing neutral current (FCNC) trans- (K ¯)exp 14 10 at 95% CL (3) itions provide a critical test of the Cabibbo-Kobayashi- Similarly, the E391a collaboration reported the 90% C.L. Maskawa (CKM) mechanism in the Standard Model upper bound [9] (SM), and allow to search for possible new physics.
    [Show full text]
  • Chargino Production in Different Supergravity Models and the Effect
    IC/96/189 SHEP–96–24 hep-ph/9609472 September 1996 Chargino Production in Different Supergravity Models and the Effect of the Tadpoles Marco Aurelio D´ıaz High Energy Section, International Centre for Theoretical Physics P. O. Box 586, Trieste 34100, Italy Abstract If the lightest chargino is discovered at LEP2, the measurement of its mass and cross section together with the mass of the lightest neutralino, enables the determination of the parameters that define the theory and the entire supersym- metric and Higgs spectrum. Within this context, we: (i) study the effect of the one–loop tadpoles in the minimization condition of the Higgs potential, by com- paring the RGE–improved Higgs potential approximation with the calculation arXiv:hep-ph/9609472v1 25 Sep 1996 of the minimum including the effect of the one–loop tadpoles, and (ii) compare the prediction of two different supergravity models, namely, the model based on B = 2m0 and motivated by the solution of the µ–problem, and the minimal supergravity model, based on A = B + m0. 1 Introduction Chargino searches at LEP1.5 at 130GeV < √s< 140 GeV center of mass energy have been negative, and new exclusion regions in the m ± m 0 plane have been published χ1 − χ1 0 [1]. For example, if mχ1 = 40 GeV and if mν˜e > 200 GeV, the chargino mass satisfy m ± > 65 GeV at 95 % C.L. Nevertheless, this bound on the chargino mass is relaxed χ1 if the lightest neutralino mass is close to the chargino mass, or if the sneutrino is lighter than 200 GeV.
    [Show full text]
  • MSSM Parameter Determination Via Chargino Production at the LC: NLO
    MSSM parameter determination via chargino produc- tion at the LC: NLO corrections Aoife Bharucha1, Jan Kalinowski2;3, Gudrid Moortgat-Pick1;2, Krzysztof Rolbiecki2 and Georg Weiglein2 1II. Institut f¨urTheoretische Physik, Universit¨atHamburg, Luruper Chaussee 149, D-22761 Hamburg, Ger- many 2DESY, Notkestraße 85, 22607 Hamburg, Germany 3Faculty of Physics, Uniwersytet Warszawski, 00681 Warsaw, Poland DOI: will be assigned Very precise measurements of masses and cross sections, with errors of < 1%, are expected to be achiev- able with a future linear collider. Such an accuracy gives sensitivity at the level of quantum corrections, which therefore must be incorporated in order to make meaningful predictions for the underlying new physics parameters. For the chargino{neutralino sector, this involves fitting one-loop predictions to expected measurements of the cross sections and forward-backward asymmetries and of the accessible chargino and neutralino masses. Our analysis shows how an accurate determination of the desired pa- rameters is possible, providing in addition access to the mass of the lighter stop. DESY 12-141 1 Introduction A linear collider (LC) will be an ideal environment for high precision studies of physics beyond the standard model (BSM). A particularly well-motivated BSM theory is the Minimal Supersymmetric Standard Model (MSSM). Fits to the latest LHC data, see e.g. [1], suggest that, if nature can indeed be described in terms of the MSSM, charginos and neutralinos could be among the lighter supersymmetric (SUSY) particles, and therefore we investigate what the LC can reveal about the structure of the chargino{neutralino sector of the MSSM. At leading order (LO), the chargino{neutralino sector can be parameterised via the gaugino masses M1 and M2, the higgsino mass µ and tan β, the ratio of the vacuum expectation values of the two neutral Higgs doublet fields, see e.g.
    [Show full text]