transverse energy

proton–proton collisions at √ s = 2.76 TeV with ATLAS The ATLAS Collaboration Abstract The relationship between jet production in the central region and the underlying-event activ- ity in a pseudorapidity-separated region is studied in 4.0 pb −1 of √ s = 2.76 TeV pp collision data recorded with the ATLAS detector at the LHC. The underlying event is characterised through measurements of the average value of the sum of the transverse energy at large pseu- dorapidity downstream of one of the protons, which are reported here as a function of hard- scattering kinematic variables. The hard scattering is characterised by the average transverse momentum and pseudorapidity of the two highest transverse momentum jets in the event. The dijet kinematics are used to estimate, on an event-by-event basis, the scaled longitud- inal momenta of the hard-scattered partons in the target and projectile beam-protons moving toward and away from the region measuring transverse energy, respectively. Transverse en- ergy production at large pseudorapidity is observed to decrease with a linear dependence on the longitudinal momentum fraction in the target proton and to depend only weakly on that in the projectile proton. The results are compared to the predictions of various Monte Carlo event generators, which qualitatively reproduce the trends observed in data but generally underpredict the overall level of transverse energy at forward pseudorapidity.

University of Virginia, Charlottesville, Virginia 22901, USA and 82 University of Washington, Seattle, Washington 98195, USA (Dated: May 25, 2009) A search for supersymmetric partners of quarks is performed in the topology of multijet events accompanied by at least one tau lepton decaying hadronically and large missing transverse energy. Approximately 1 fb −1 of p¯ p collision data from the Fermilab Tevatron Collider at a center of mass energy of 1.96 TeV recorded by the D0 detector is analyzed. Results are combined with the previously published D0 inclusive search for squarks and gluinos. No evidence of physics beyond the standard model is found and lower limits on the squark mass up to 410 GeV are derived in the framework of

We present a search for the pair production of scalar top quarks, ˜ t, using 995 pb −1 of data collected in p¯ p collisions with the D0 detector at the Fermilab Tevatron Collider at √ s = 1.96 TeV. Both scalar top quarks are assumed to decay into a charm quark and a neutralino ( ˜ χ 0 1 ), where ˜ χ 0 1 is the lightest supersymmetric particle. This leads to a final state with two acoplanar charm jets and missing transverse energy. We find the yield of such events to be consistent with the standard model expectation, and exclude sets of ˜ t and ˜ χ 0

PACS numbers: 25.75.Dw I. INTRODUCTION Systematic measurements of the centrality dependence of transverse energy production and charged particle multiplicity at midrapidity provide excellent character- ization of the nuclear geometry of the reaction and are sensitive to the dynamics of the colliding system. For ex- ample, measurements of dNch/dη and dET /dη in Au+Au collisions at √s N N = 200 GeV and 130 GeV as a func- tion of centrality expressed as the number of participant nucleons, Npart, exhibit a nonlinear increase with increas- ing Npart. This has been explained by a two-component model proportional to a linear combination of the num- ber of collisions, Ncoll, and Npart [1, 2]. In a previous study by the PHENIX collaboration, measurements of dET /dη and dNch/dη for Au+Au collisions at 200, 130, and 62.4 GeV are presented along with comparisons to the results of several models [3]. The models that were examined included HIJING [4], a final state parton sat- uration model called EKRT [5], an initial state parton saturation model called KLN [2], and a multiphase trans- port model called AMPT [6]. The comparisons showed that most models could reproduce some of the features of the data, but most failed in describing all of the data with the HIJING and AMPT models best describing the

Measurements of transverse energy–energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used corres- pond to √ s = 8 TeV proton–proton collisions with an integrated luminosity of 20.2 fb −1 . The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the run- ning of α s (µ) predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy–energy correlation distributions yields α s (m Z ) = 0.1162±0.0011 (exp.) +0.0084 −0.0070 (theo.), while a global fit to the asymmetry distributions yields a value of α s (m Z ) = 0.1196 ± 0.0013 (exp.) +0.0075 −0.0045 (theo.).

Abstract. Making use of 36 pb − 1 of proton-proton collision data at √ s = 7 TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95 % Confidence Level (CL) upper limit is set on the cross section for new physics of σ < 0.38 − 0.65 pb in the context of a generalised model of gauge mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of σ < 0.18 − 0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95 % CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a lower limit of 1/R > 961 GeV is set on the UED compactification radius R. These limits provide the most stringent tests of these models to date.

High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy–energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 pb −1 . The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next- to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the Z boson mass is determined to be α s (m Z ) = 0.1173 ± 0.0010 (exp.) +0.0065 −0.0026 (theo.).

data and MC, for which the primary vertex position, z PV , serves the role of z DCA . B. Timing resolution Photons from NLSP decays would reach the LAr calorimeter with a slight delay compared to prompt pho- tons. This delay results mostly from the flight time of the heavy NLSP, as well as some effect due to the longer ge- ometric path of a non-pointing photon produced in the NLSP decay. The EM calorimeter, with its novel “ac- cordion” design, and its readout, which incorporates fast shaping, has excellent timing performance. Quality con- trol tests during production of the electronics required the clock jitter on the LAr readout boards to be less than 20 ps, with typical values of 10 ps [26]. Calibra- tion tests of the overall electronic readout performed in situ in the ATLAS cavern show a timing resolution of ≈ 70 ps [27], limited not by the readout but by the jit- ter of the calibration pulse injection system. Test-beam measurements [28] of production EM barrel calorimeter modules demonstrated a timing resolution of ≈ 100 ps in response to high energy electrons.

38 Moscow State University, Moscow, Russia 39 Institute for High Energy Physics, Protvino, Russia 40 Petersburg Nuclear Physics Institute, St.. Petersburg, Russia.[r]

and gluino masses, and the NLO cross section. The uncertainty coming from the JES corrections is typically (10–15)% for the SM backgrounds and (6–11)% for the signal efficiencies. The uncertainties due to the jet energy resolution, to the jet track confirmation, and to jet reconstruction and identification efficiencies range between 2% and 4%. All these uncertainties on jet prop- erties account for differences between data and MC sim- ulation, both for signal efficiencies and background con- tributions. The trigger was found to be fully efficient for the event samples surviving all analysis cuts with an uncertainty of 2%. The uncertainty on the luminosity measurement is 6.1% [21]. All of these uncertainties are fully correlated between signal and SM backgrounds. A 15% systematic uncertainty was set on the W/Z+jets and t¯ t NLO cross sections. The uncertainty on the signal acceptance due to the PDF choice was determined to be 6%, using the forty-eigenvector basis of the CTEQ6.1M PDF set [11]. Finally, the effects of ISR/FSR on the signal efficiencies were studied by varying the pythia parameters controlling the QCD scales and the maximal allowed virtualities used in the simulation of the space- like and time-like parton showers. The uncertainty on the signal efficiencies was determined to be 6%.

ments are applied on the fraction of energy deposited in the EM calorimeter and on isolation in both the calorime- ter and the tracker. The shower width in the third layer (EM3) must be consistent with that of a photon. To sup- press electrons misidentified as photons, the candidates must not be spatially matched to a track or to energy de- positions in the silicon microstrip or central fiber trackers that lie along the trajectory of an electron [12]. Fur- ther rejection of jets is achieved with a NN discriminant similar to that used for electron selection. The average identification efficiency for photons with p T = 40 GeV is

Index Terms— Single-photon imaging, depth imaging, convex optimization, greedy algorithm, LIDAR, Poisson processes 1. INTRODUCTION The technique of light detection and ranging (LIDAR), which typi- cally uses a pulsed, narrow-beam light source and a photodetector, reconstructs scene depth by measuring the time-of-flight (ToF) of the backreflected return from each pixel [1]. If there are multiple reflections from the scene, such as when imaging through a scat- tering medium, then multiple times-of-flight are recorded for multi- depth reconstruction [2]. By transverse-scanning the light source and repeating the pixelwise ToF acquisition process, one can obtain a spatially-resolved depth profile of a scene.

of being predominantly unstable for t ∼ T ε . An energy estimate on U − U ap will then be used. This is particularly important ensure that the time of existence of U is large enough to get the desired amplification, as we only have local existence for solutions to (1) (see S. Benzoni, R. Danchin and S. Descombes in [3]). Article [3] also provides a blow- up criterion, but the instability phenomenon is not related to the blow-up if it occurs; indeed, the mechanism is also observed on systems that have global solutions (most of the previous examples, whether they concern boundary layer or solitary wave instability, fall in this category). Finally, combining the two will lead to the instability result.

In this paper we have studied the transverse fluctuations in quasi-1D systems of particles in a thermal bath, near the zigzag transition. We have demonstrated that close to the zigzag threshold, the transverse fluctuations exhibit the typical SFD behavior, with a MSD that scales as the square root of time. This subdiffusive behavior traces back to strong interparticle correlations, and is observed on both sides of the transition. In contrast with the longitudinal fluctuations, for which the correlations are due to the noncrossing condition, the transverse motions of the particles are only correlated close to the zigzag transition. Their dynamics is closely linked to the overdamped modes in the vicinity of the soft mode that appears at the transition, and replaces the zero frequency mode due to translational invariance for longitudinal motion [ 5 , 15 ].

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Key words: Reinforced Concrete, Shear Strengthening, Shear Behaviour, Shear Strength, Unbonded.. 24.[r]

Une connaissance précise des conditions aux limites tant aérodynamiques que thermiques se justifie d'une part, par la vérification de la qualité des écoulements en amont et de la chauffe du matériau de test, mais aussi par l'exploitation numérique du problème. Des mesures LDA sont effectuées dans l'écoulement transverse en amont de la sortie du jet (plan "entrée" de la figure 2) suivant deux lignes (y=0 et z=½ hauteur veine). Aucune influence de la présence du jet ou d'une modification du débit de celui-ci n'est détectée. Les profils complets finaux de vitesse et d'énergie turbulente extrapolés à partir des données LDA (figure 3) restent donc stationnaires au cours du transitoire et peuvent être directement exploités dans le modèle numérique. Pour le jet, des difficultés d'accès optique nous ont contraints à réaliser les mesures LDA à 3 mm en aval du plan de sortie de buse. Le maillage exploratoire est constitué de 378 points et il déborde les limites du jet d'un rayon. La vitesse w de soufflage est assez uniforme même si à cette distance le jet est déjà affecté par la présence de l'écoulement transverse : la symétrie cylindrique est perdue même si la composante de cisaillement u est faible.

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At variance with the TM, the phase space has a structure, and each state has N neighbours whose energies, as we show in Sec. A.1, Eq. (34), typically lie in the interval I ≡ h − √ 2N ln N , √ 2N ln N i . (13) The majority of states have at least one lower neighbour, and the dynamics spends little time there, since the Metropolis update rule [Eq. (4)] privileges energy descent. As a consequence, the states in which most of the time is spent are those without a lower neighbour, which have energy

Finally, the density of charged particles in y-φ space, ρ ch (r, p T jet ), is measured as a function of the angular dis- 1 ATLAS uses a right-handed coordinate system with its ori- gin at the nominal interaction point (IP) in the centre of the detector and the Z-axis coinciding with the axis of the beam pipe. The X-axis points from the IP to the centre of the LHC ring, and the Y -axis points upward. Cylindrical coordinates (r,φ) are used in the transverse plane, φ being the azimuthal angle around the beam pipe. The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2). The rapidity y for a track or jet is defined by y = 0.5 ln [(E + p Z )/(E − p Z )]