DOCSLIB.ORG

University of Stockholm Institute of Physics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
University of Stockholm Institute of Physics UNIVERSITY OF STOCKHOLM INSTITUTE OF PHYSICS HIGGS BOSON EVENTS AND BACKGROUND AT LEP A MONTE CARLO STUDY G. EKSPONG and K. HULTQVIST USD? Report 82 - 05 June 1982 US., f* -- S2. -o HIGGS BOSON EVENTS AND BACKGROUND AT LEP A Monte Carlo Study G. EkspongandK. Hultqvist Department of Physics, University of Stockholm Vanadisvägen 9, S-113 46 Stockholm ABSTRACT + - 0 0 + - Higgs boson production at LEP using ee **Z -* H +ee has A " i studied by Monte Carlo generation of events with realistic errors of me re ment added. The results show the recoil mass (Higgs boson mass) resolution '•> be reason- ably good for boson masses £ 5 GeV. The events are found to populate a phase space region free of , jysical back- ground for all boson masses below about 35 GeV. For masses Above 40 GeV the Higgs boson signal merges with the physical background pi .iuced by semi- leptonic decays of heavy flavour quarks while diminishing in sti ongth to low levels. The geometrical acceptance of a detector like DELPHI is about 80% for Higgs boson events. 1. INTRODUCTION In the standard electrovvrak theory (Ref. 1) spontaneous symmetry breaking is achieved by the Higgs mechanism. One neutral Higgs boson with known couplings appears in the theory as a challenge for experimental researchers. Its mass has not been predicted. Methods which cover as wide a range in mass as possible are therefore valuable. It has been pointed out (Ref. 2) that the reaction 0 0 + e e •* Z -»H 4 p + i (i) is quite favourable for not too heavy Higgs bosons (H ). The signature in an event for reaction (i) is two fast leptons (e:s or p-.s) with high invariant mass and many particles arising in the decay of the Higgs boson. The method would be to look for a peak in the missing mass recoiling against the two fast leptons, and after finding it to look into the detailed composition of the decay products. In the absence of errors and background the recoil mass would be equal to the Higgs boson mass. We have applied Monte Carlo methods for simulating events according to re- action (i) and to add realistic errors of measurement to the observed tracks. In this way the mass resolution for various assumed boson masses has been obtained and also the expected geometrical acceptance of a proposed detector (DELPHI, Ref. 3, Fig. 1) The physical background from the semi-leptonic decays of heavy quarks pro- duced by Z "*qq, has also been studied by us in great detail using Monte Carlo methods. A scatterplot of recoil mass versus invariant dilepton mass in each event is very useful for separating the signal (Higgs boson events) from the background. Studies of these or similar questions have been carried out earlier (Ref:s 4 & 5). The results of Ref. 4 is, however, at variance with ours in that we find a better mass resolution for the recoil mass and a different range of detectable boson masses. Our methods of analysis and of background simulation are different and more detailed. 2. F UNDA ME NT A L RE LA TION S Finjord (Ref. 6) gives the following expression for the differential rate for G M (C tC r F 7 T R> V 9 9 9 , 9 , —9 ^ ^—9^ " -9 —X (1,/i ,x )(2x +-X(1,/i ,x )) (ii) dx" 192 7T ((x"- 1 -L )" * A ) In this formula x = M + -/AL,, where M •+ - is the effective mass of the e e Z oe e e e -pair, a is the relative width of Z and /x = M,, /Mz is the relative mass of the Higgs boson. The scale factor 2 5 2 2 GFMZ(CL + CR} 192TT3 2 varies with sin 6 . W Integration of (ii) yields the total rate. As can be seen from Fig. 2 this drops rapidly with increasing M (Ref. 6). H If p, k, p1 and k1 are the four-momenta of the incoming and outgoing e and e , respectively, then, neglecting V-A interference, the matrix element squared contains the factor ,2 |M| OC [(pkI)(p'k) + (pp1)(kk1)] . (iii) (Ref. 7) This gives a total differential rate 5 2 d r G^ycR^xW.* ) /2 2 2 „ —2 rr-= r-^-r—5 \y M-icos ©cos 6 _ eH dx d(cose)dpd(cos8 )d<peH 2 rr [(x 1+^") ^ ] 22 2 2 _2 2 2i i2>fcos0sin0cos8 sin6 co«p + sin ösin 6 ..cos (p -y j3^(cos S+cos 6 ) (iv) e Hu eH eH eH erl eH , where j3 and y are the velocity and Lorentz-factor, respectively, for the e e - -pair in CMS. The angles are defined in Fig.3. Formula (ii) can be rederived by integrating over the angles. 3. RATES The cross section for e e -*Z -* visible states (excluding w and Bhabas) at the energy of the Z peak is (Ref. 8): + - 0 ff(e e "*Z . ) = 2600ff (v) vis pt where O is the point-like QED cross section. For Vs = 90 GeV = M this is O '- 10.7 pb . pt 30 -1 _2 Assuming a luminosity of 6 • 10 s cm , one year's running (2500 h) gives an integrated luminosity of 54 pb , or 1.5- 106 Z°/yr . Using B(Z -» e e ) 3.71% (for the visible Z :s) one obtains the following average number of reactions of type (i) in a one year run- Table 1 Higgs boson mass (GeV) 5 10 15 20 25 30 40 n:o of events 223 127 79 51 33 22 9 4. THE MONTE CARLO GENERATION OF EVENTS We generated the events according to formula (iv), using M - 90 GeV with a width of 3 GeV. Because of the axial symmetry the tp dependence is trivial, tp beeing uniformly distributed between 0 and 2 n. The remaining four-dimensional generation problem was reduced to four suc- cessive one-dimensional ones. This was done by keeping the variables already generated fixed, while integrating out the ones not yet to be generated, thus obtaining a conditional and marginal distribution in the wanted variable, x. The distribution obtained, dN/dx, was normalized to one: 00 dN , — dx 1 dx Generating a random number, £, uniformly distributed between 0 and 1 and choosing x to fulfil x dN N(x) = — (V!) gives x-values with the desired distribution. The first variable we generated was X (= M + -/M,,). Integrating over all e e Z angles gives the cumulative distribution X dIYJV2 2xdx (VU) J dF 2 where /dx is given in formula (ii). For each Higgs boson mass N(X) was calculated numerically for 300 values of X. For each event a £ was generated and equation (vi), N(x) = % , was solved for x by linear interpo- lation . With x fixed to this value cos© was generated according to the same prin- eH ciple. Integrating over (f> and cosö and normalizing one obtains the distri eH bution dN * A 2fl d(cos6 ) A -++ A cos 8eH where 2 A 3(1 ±y ) ±~ 2 4(2^ y ) Equation (vi) now reads : 3A 3 + 3 e8(A This third degree polynomial equation in cos8 rT was solved algebraically. Keeping x and cos6 fixed gives a similar expression for cos© : 6*1 dN 2fi d(cos8) A t A cos ö This time, however, 3(cos26 -t 1 i 2>2(1-cos2e )) ± = 2 2 2 8 (cos 8 + 1 + y (1 - cos 8 )) The resulting equation for cos6 is the same as (viii) for cos8 arl was solved in the same way. Keeping X.cosS and cos© fixed the cumulative distribution in <p is 6x1 6ri NW>eH> = U<PeH where U = ^ V 2yc0SeeHsineeH cose sine eH N = 2 [y2 + r2cos2$ cos2ö-(y2- 1) (cos2© +cos2ö)] -f sin2e sin2© 6rl G*i Cxi N((p ) = Equation (vi) eH ^ ' was now solved numerically. Finally a Lorentz boost and a rotation yields the four-momentum of the electron in CMS (with the z-axis parallel to the beam): M cos6 Pz = 2 z [V( eH-0) cose + sineeHcos<PeHsin$] pv = •- IVf [y(cos& -0) sin8 cos<p-(cos8Cos<pcos(p -sin<p sinp ) sin© j j\ z Z eti 6n en eri pv ~ - M [y(cos8 -/5) sin6sin<p-(cos6sin<Pcos(p tcosipsin(p )sin6 ] (x) The positron momentum is obtained by the transformation 6 -* ir - 6 eH eH ** Tt t 5. PROCESSING OF THE GENERATED EVENTS We studied the detection of the generated events in the DELPHI detector. All events with both electron and positron passing through an electromagnetic calorimeter were accepted. The acceptance was found to be 80%, and is independent of M (see Fig. 4). H The barrel calorimeter accepts about 50% of the events and the end cap calori- meter adds about 30%, either alone or in combination with the barrel. Normally distributed errors were added to the energies with AE JO. 10 forward calorimeter r? I 0.11 barrel calorimeter v hi We also added errors to the angles using £0 - A^> - 0.4 mrad for tracks passing through the forward chambers and Afl -- A<p =1.5 mrad elsewhere. The errors in energy are the dominating ones. 6. SINGLE PARTICLE DISTRIBUTIONS The single-electron energy spectrum for M = 10 GeV is shown in Fig. 5. It is H peaked at high energies (~40 GeV). The electromagnetic calorimeters in DELPHI give a good measurement of these high electron energies. For muons the situation is different, and for energies above 15 GeV the precision is better for electrons. This is the reason for using the reaction Z -• H e e , rather than Z° - H°MV- 2 The electron angular distribution has a (1 •+ Acos 6) shape (Ref.
Load more

Recommended publications
  • LD2668T41961L36.Pdf
    CARBC^IA-CONTAINIMG CGHFOUKDS PRODUCED BI THE PILE-SEOTRQH IRRADIATIGH OP CYAHOGUANIDIIE THOMAS WILLIAM LAPP * B.A., Co* College, 1959 A MAS TBI'S THESIS . submitted in partial fulfillment of the requirements for the degree MASTER 07 SCIENCE Department of Chemistry KANSAS STATE UNIVERSITY Manhattan, Kansas 1%1 TABLE OP COHTKHTS INTRODUCTIOU 1 Theoretical Considerations 3 Previous llH(n,p)cU studies 10 EXPERIMENTAL 21 Sample Preparation. 21 Irradiation of the Cyanoguanidine Sample. • 21 Analysis of the Irradiated Sample 23 Total Carbon-U Activity 25 Chemical Separations 25 Radiochemical Counting Techniques 31 RESULTS AND DISCUSSION 37 Distribution of the Carbon-14 Recoil Atom 40 Radiocarbon Product Distribution 46 SUMMARY 50 ACKNOWLEDGMENTS 51 REFERENCES 52 t nmtCLXTroi In a flux of thermal neutrons, nitrogen atone undergo the nuclear trine- formation NH(n>p)cH. in normal pile-neutron irradiations, the compound to be Irradiated is also subjected to gamma radiation. Both the gamma radia- tion and the nuclear reactions initiated by the neutrons are capable of supplying energy to promote chemical reactions which normally would occur only at elevated temperatures. Collins and Calkins (6) have estimated the average energy of the gamma rays in the Oak Ridge graphite reactor to be approximately 1 Mev. Few nuclear reactions are initiated by the absorption of gamma rays at this photon energy and thus, the important nuclear reactions are those produced by the neutrons. The eyanoguanidine molecule is interesting for studying the chemical consequences produced by the nuclear transformation NU( n ,p)cH for two reasons (1) Within the eyanoguanidine molecule, the nitrogen atoms are bound to carbon atoms by three different types of bonding: single, double and triple bonds.
    [Show full text]
  • The New Look in Oil-Mud Technology
    DISPERSIBLE COLLOIDS The New Look in Oil-Mud Technology JAY P. SIMPSON MEMBER AIME BAROID DIV., NATIONAL LEAD CO. Downloaded from http://onepetro.org/jpt/article-pdf/13/12/1177/2213517/spe-150-pa.pdf by guest on 27 September 2021 J. C. COWAN HOUSTON, TEX. A. E. BEASLEY, JR. Abstract tributed to the general inflexibility of the systems. This inflexibility resulted primarily because one basic component Liquids having oil as the continuous phase long have was used in an attempt to arrive at all mud properties. been recognized as desirable for drilling and completing These oil systems can be compared with the early water­ under certain conditions. Performance limitations, high base muds. costs and inconvenience of handling, however, have kept these oil muds from becoming accepted for widespread, Water-base mlfds in the early years of drilling depended general use. upon bentonite for rheological properties, suspension of solids and filtration control. As was learned with these As previously used, the muds consisted of a bodying earlier clay-water systems, one basic component cannot agent for oil, or primary emulsifier of water in the oil, and by itself provide all of ideal drilling-fluid properties. Today a series of supplementary additives to modify that principal each water-base drilling-fluid property can be controlled component. In recent years a new approach to oil muds with an exactness that was not believed possible even 10 has been taken. Oil-dispersible colloids have been developed years ago. Water-base muds are prepared to have certain to perform specific functions in oil without dependence properties to serve specific purposes, some examples of upon thickening of the oil or emulsification of water.
    [Show full text]
  • Download Author Version (PDF)
    PCCP Accepted Manuscript This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/pccp Page 1 of 12Journal Name Physical Chemistry Chemical Physics Dynamic Article Links ► Cite this: DOI: 10.1039/c0xx00000x www.rsc.org/xxxxxx ARTICLE TYPE Estimating the Binding Ability of Onium Ions with CO 2 and π Systems: A Computational Investigation M. Althaf Hussain, A. Subha Mahadevi and G. Narahari Sastry* Manuscript Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX 5 DOI: 10.1039/b000000x Density functional theory (DFT) calculations have been employed on 165 complexes of onium ions + + + + (NH 4 , PH 4 , OH 3 ,SH 3 ) and methylated onium ions with CO 2, aromatic (C 6H6) and heteroaromatic (C 5H5X, X = N, P; C 4H5Y, Y = N, P; C 4H4Z, Z = O, S) systems.
    [Show full text]
  • A Probabilistic QCD Picture of Diffractive Dissociation and Predictions for Future Eics
    A probabilistic QCD picture of diffractive dissociation and predictions for future EICs Anh Dung Le Based on: ADL, Mueller & Munier, PRD 103 (2021) 054031 ADL, Mueller & Munier, ar iv:2103"100## ADL, arXi!:2103"0$$24 Presen%ed at RPP2021 MO I!A ION + A QCD pi.%ure for diffra.%ion and partonic le!el + Predic%ions a% /u%ure ele.%ron-ion colliders (EICs) 4'ser!a'le of interes%: Rapidity-gap distribution! Diffraction at #ERA$ A large angular ga& obser!ed( Large ra&idity ga& (LRG) 2 CON E" ) 3" DIS in dipole 6odel and diffra.%ion 33" Diffra.%i!e disso.ia%ion of oniu6: a proba'ilis%ic ,CD &ic%ure 333" Diffra.%ive disso.ia%ion a% /u%ure EICs 3 QCD dipole *odel for DI) 7ir%ual photon probes nu.leus !ia a quark-an%iquar9 .olor single% dipole (oniu6) Dipole /a.%oriza%ion: Proba. of the splitting virtual photon → dipole :;: momen%um frac%ion of &hoton carried b) quar9 (or an%i8uark)] 4 Diffractive dissociation of virtual p+oton 2!ol!ed s%a%e 'y Q-D radiati!e e6issions Photon disso.iated to a se% o/ &arti.les (X) > angular gap in de%e.%ors =u.leus ke&% in%ac% 5 Diffractive dissociation of onium 6 Color dipole evolution: )oft-gluon e*issions I0 I0 r Large N 1 ?igh-ra&idi%) e!olu%ion I . I 2 r 2 Transverse position rk r2 space I1 I1 Large nu6'er o/ colors (N.) li6i%: gluon ≃ ;ero1si;e quar91an%i8uark pair @ one1gluon e6ission ≃ (1A 2) di&ole bran.hing (L4; soH1gluon a&&roI.) Boos%ing to high rapidi%y B: 1 Bran.hing re&ea%ed (and inde&enden%) → 'ran.hing &ro.ess 1 Coc9 s%ate of oniu6 is a se% of di&oles wi%h random si;es {r9F A random num'er densi%) n(r9) Each event recorded in a detector corresp.
    [Show full text]
  • SANTA CRUZ INSTITUTE for PARTICLE PHYSICS LIST of PREPRINTS SCIPP # 1. Finite Size Scaling and Asymptotic Freedom of the SU(2)
    SANTA CRUZ INSTITUTE FOR PARTICLE PHYSICS LIST OF PREPRINTS SCIPP # 1. Finite Size Scaling and Asymptotic Freedom of the SU(2) Lattice Gauge Model, M. Nauenberg, T. Schalk and R. Brower, Phys. Rev. D24:548 (1981) 81/1 2. Cosmic Ray Trigger Circuit for Large Solenoidal Particle Detectors, A. Seiden, P. Shaffer and J. Warner, NIM 193:597 (1982) 81/2 3. Elastic Photon-Photon Scattering in the 50-130 GeV Range, A.M. Breakstone et al., Phys. Rev. Lett. 47:1778 (1981) 81/3 4. Quasi-Elastic Omega Photoproduction at 50-130 GeV, A.M. Breakstone et al., Phys. Rev. Lett. 47:1782 (1981) 81/4 5. Large Drift Chambers with a Multi-Wire Cell Design, F. Grancagnolo and A. Seiden 81/5 6. A Large-Solid-Angle Spectrometer for High Energy Electrons and Photons, A.M. Breakstone, C.A. Heusch and A. Seiden, NIM 211:209 (1983) 81/6 7. The SU(2) Adjoint Higgs Model, R.C. Brower et al., Phys. Rev. D25:3319 (1982) 81/7 8. Some Ideas on a Central Tracking Chamber for the SLAC Linear Collider, A. Seiden, Proceedings of the 2nd 81/8 TRISTAN Physics Workshop, KEK, Tsukuba, Japan; Ed. Y. Unno, KEK 82-1, p.466 (May 1982) 9. Heavy Flavor Production from Photons and Hadrons, C. Heusch, Presented at the SLAC Summer Institute 82/9 on Particle Physics, 1981. 10. Wide Angle Secondaries Produced by `Beamstrahlung' Interactions, D.B. Smith (SLC Report). 82/10 11. Central Tracking Chamber for SLC, A. Seiden (SLC Report) 82/11 12. Tradeoffs in Drift Chamber Design, A.
    [Show full text]
  • Deep-Inelastic Onium Scattering
    DAPNIA/SPP 95-15 SPhT-T95-090 Deep-Inelastic Onium Scattering H.Navelet1, R.P eschanski1,Ch.Royon2 1- Service de Physique Th´eorique, Centre d’Etudes de Saclay F-91191 Gif-sur-Yvette Cedex (France) 2- DAPNIA - SPP, Centre d’Etudes de Saclay F-91191 Gif-sur-Yvette Cedex (France) Abstract: Using the colour dipole approach of the QCD per- turbative (BFKL) Pomeron exchange in onium-onium scattering, we compute the cross section for small but hierarchically different onium sizes. A specific term dependent on the size-ratio is gener- ated. In deep inelastic onium scattering it appears as a scaling- violation contribution to the quark structure function near the BFKL singularity. We find that the extension of the formalism for deep inelastic onium scattering to the proton structure func- tion provides a remarkably good 3-parameter fit to HERA data at small x with a simple physical interpretation in terms of the dipole formulation. 1 Recently, a dipole model approach to the QCD computation of onium- onium scattering from the perturbative resummation of leading logarithms has been proposed[1, 2, 3]. In this framework, each onium state describes a small (i.e. massive) colour-singlet quark-antiquark pair whose infinite mo- mentum wavefuntion is itself composed of colour dipoles at the moment of the interaction. These onia interact locally in impact-parameter space via 2-gluon exchange between the component dipoles. The overall total cross-section has been shown to reproduce the well-known[4] QCD Pomeron exchange (BFKL) due to leading log 1/x resummation. It is thus tempting to try and apply this formalism to the deep-inelastic scattering off protons and more specifically to the proton structure function measured at HERA[5].
    [Show full text]
  • Diffractive Dissociation in Future Electron-Ion Colliders
    1 INTRODUCTION Diffractive dissociation in future electron-ion colliders Anh Dung Le?, CPHT, CNRS, École polytechnique, IP Paris, F-91128 Palaiseau, France * [email protected] August 2, 2021 Proceedings for the XXVIII International Workshop on Deep-Inelastic Scattering and Related Subjects, Stony Brook University, New York, USA, 12-16 April 2021 doi:10.21468/SciPostPhysProc.? Abstract We study diffractive scattering cross sections, focusing on the rapidity gap distribution in realistic kinematics at future electron-ion colliders. Our study consists in numerical solu- tions of the QCD evolution equations in both fixed and running coupling frameworks. The fixed and the running coupling equations are shown to lead to different shapes for the rapid- ity gap distribution. The obtained distribution when the coupling is fixed exhibits a shape characteristic of a recently developed model for diffractive dissociation, which indicates the relevance of the study of that diffractive observable for the partonic-level understanding of diffraction. 1 Introduction Single diffractive dissociation in electron-hadron collisions is defined to be the scattering process in which the virtual photon mediating the interaction fluctuates into a set of partons part of which goes in the final state while the hadron remains intact, leaving a large rapidity gap between the latter and the slowest produced particle. The rapidity gap characterization of diffractive events is manifested in collision experiments by the existence of a large angular sector in the detector arXiv:2107.14511v1 [hep-ph] 30 Jul 2021 with no measured particle. Such events were first observed in electron-proton collisions at DESY HERA [1,2 ], and their detailed analysis is one of goals of the construction of future electron-ion colliders [3–5].
    [Show full text]
  • Investigating Extreme Ultraviolet Radiation Chemistry with First-Principles Quantum Chemistry Calculations
    Investigating extreme ultraviolet radiation chemistry with first-principles quantum chemistry calculations a,b c c Jonathan H. Ma, Han Wang, David Prendergast, a,d a, Andrew Neureuther, and Patrick Naulleau * a Lawrence Berkeley Laboratory, Materials Sciences Division, Center of X-Ray Optics, Berkeley, California, United States b University of California Berkeley, Department of Physics, Berkeley, California, United States c Lawrence Berkeley Laboratory, Molecular Foundry, Berkeley, California, United States d University of California Berkeley, Department of Electrical Engineering and Computer Science, Berkeley, California, United States Abstract. In extreme ultraviolet (EUV) lithography, chemistry is driven by secondary elec- trons. A deeper understanding of these processes is needed. However, electron-driven processes are inherently difficult to experimentally characterize for EUV materials, impeding targeted material engineering. A computational framework is needed to provide information for rational material engineering and identification at a molecular level. We demonstrate that density func- tional theory calculations can fulfill this purpose. We first demonstrate that primary electron energy spectrum can be predicted accurately. Second, the dynamics of a photoacid generator upon excitation or electron attachment are studied with ab-initio molecular dynamics calcula- tions. Third, we demonstrate that electron attachment affinity is a good predictor of reduction potential and dose to clear. The correlation between such calculations and experiments suggests that these methods can be applied to computationally screen and design molecular components of EUV material and speed up the development process. Keywords: extreme ultraviolet lithography; extreme ultraviolet exposure chemistry; photoacid generator chemistry; radiation chemistry; extreme ultraviolet fundamentals. 1 Introduction With the introduction of extreme ultraviolet (EUV), electron-driven processes in photoresists 1 become relevant.
    [Show full text]
  • Thesis, We Take Σψ Directly from Experimental Data
    QUARKONIUM TRANSPORT THEORY IN ULTRA-RELATIVISTIC HEAVY-ION COLLISIONS A Dissertation by XIAOJIAN DU Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Ralf Rapp Committee Members, Siu Ah Chin Che-Ming Ko Saskia Mioduszewski Frank Sottile Head of Department, Grigory Rogachev August 2019 Major Subject: Physics Copyright 2019 Xiaojian Du ABSTRACT The study of the fundamental strong interaction is an important vehicle for advancing our understanding of nuclear physics. Quarkonia, bound states of heavy quark-antiquark pairs, are promising probes for studying the strong force, in particular its confining prop- erty which constrains quarks and gluons to hadrons. Ultrarelativistic heavy-ion collisions (URHICs) are the only experimental method that can screen the strong force by creating a hot and dense medium. The suppression of quarkonia observed in URHICs is believed to be due to the formation of a deconfined quark-gluon plasma (QGP), a medium with un- bound quarks and gluons. In order to study this phenomenon, we utilize a transport model to describe the evolution of quarkonium states in URHICs. This model calculates the sup- pression of heavy quarkonia, as well as recombination of heavy quark-antiquark pairs, in the medium. For charmonium, in particular, the recombination is essential for describing the momentum and energy dependencies of their spectra. Based on the fact that different binding energies lead to different dissociation temperatures, a “sequential regeneration” of excited and ground-state charmonia is proposed and implemented to compare to experi- mental data in nuclear collisions.
    [Show full text]
  • Quantum Phase Transition and Degeneracy of a Circuit-QED Vacuum Pierre Nataf, Cristiano Ciuti
    Quantum phase transition and degeneracy of a circuit-QED vacuum Pierre Nataf, Cristiano Ciuti To cite this version: Pierre Nataf, Cristiano Ciuti. Quantum phase transition and degeneracy of a circuit-QED vacuum. 2009. hal-00418515v1 HAL Id: hal-00418515 https://hal.archives-ouvertes.fr/hal-00418515v1 Preprint submitted on 18 Sep 2009 (v1), last revised 15 Jan 2010 (v3) HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Quantum phase transition and degeneracy of a circuit-QED vacuum 1 1, Pierre Nataf and Cristiano Ciuti ∗ 1Laboratoire Mat´eriaux et Ph´enom`enes Quantiques, Universit´eParis Diderot-Paris 7 and CNRS, Bˆatiment Condorcet, 10 rue Alice Domont et L´eonie Duquet, 75205 Paris Cedex 13, France We investigate theoretically the quantum vacuum properties of a transmission line resonator inductively coupled to a chain of N superconducting qubits. We derive the quantum Hamiltonian for such circuit-QED system, showing that, due to the type and strength of the interaction, a quantum phase transition occurs in the limit of large N, with a twice degenerate quantum vacuum above a critical coupling. The phase diagram can be fully explored thanks to the controllable ultrastrong coupling of the qubits with the modes of the transmission line resonator.
    [Show full text]
  • The University of Chicago Quantum Computing with Distributed Modules a Dissertation Submitted to the Faculty of the Division Of
    THE UNIVERSITY OF CHICAGO QUANTUM COMPUTING WITH DISTRIBUTED MODULES A DISSERTATION SUBMITTED TO THE FACULTY OF THE DIVISION OF THE PHYSICAL SCIENCES IN CANDIDACY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF PHYSICS BY NELSON LEUNG CHICAGO, ILLINOIS MARCH 2019 Copyright c 2019 by Nelson Leung All Rights Reserved TABLE OF CONTENTS LIST OF FIGURES . vi LIST OF TABLES . viii ACKNOWLEDGMENTS . ix ABSTRACT . x PREFACE............................................ 1 1 QUANTUM COMPUTING . 2 1.1 Introduction to Quantum Computing . .2 1.2 High-Level Description of Some Quantum Algorithms . .3 1.2.1 Grover’s algorithm . .3 1.2.2 Shor’s algorithm . .3 1.2.3 Variational Quantum Eigensolver (VQE) . .4 1.3 Quantum Architectures . .4 1.3.1 Trapped Ions . .4 1.3.2 Silicon . .5 1.3.3 Superconducting qubits . .5 1.4 Thesis Overview . .6 2 CIRCUIT QUANTUM ELECTRODYNAMICS . 7 2.1 Quantization of Quantum Harmonic Oscillator . .7 2.2 Circuit Quantum Harmonic Oscillator . 10 2.3 Josephson Junction . 12 2.4 Quantization of Transmon Qubit . 13 2.5 Quantization of Split Junction Transmon Qubit with External Flux . 16 2.6 Coupling between Resonators . 18 2.7 Dispersive Shift between Transmon and Resonator . 21 3 CONTROLLING SUPERCONDUCTING QUBITS . 23 3.1 Charge Control . 23 3.2 Flux Control . 25 3.3 Transmon State Measurement . 25 3.4 Cryogenic Environment . 26 3.5 Microwave Control Electronics . 26 3.5.1 Oscillator . 26 3.5.2 Arbitrary waveform generator . 27 3.5.3 IQ mixer . 27 3.6 Other Electronics . 28 3.7 Microwave Components . 28 3.7.1 Attenuator .
    [Show full text]
  • Lawrence Berkeley Laboratory UNIVERSITY of CALIFORNIA
    t.,t(> ~Yd LBL- 2 0 7 4 7 ~ I Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA 1 . '' r, ·) t· Physics Division ·• ... ' ;..; ;] 1986 :BRARY AND -"'TS S'=r..,...f('" • Lectures given at the Summer School on 'Architecture of Fundamental Interactions', Les Houches, France, July-August 1985 THE QUEST FOR SUPERSYMMETRY I. Hinchliffe December 1985 - Prepared for the U.S. Department of Energy under Contract DE-AC03-76SF00098 DISCLAIMER This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California. "") •.~ t ~ -- December 1985 LBL-20747 Table of Contents 1. Introduction THE QUEST FOR SUPERSYMMETRY* 2. Cosmological Bounds 3. Supersymmetry in e+ e- Annihilation Lectures given at the Summer School on 'Architecture of Fundamental 4.
    [Show full text]