Jet and photon measurements from ATLAS

Di erential cross-section measurements of inclusive-jet and di-jet production provide stringent tests of perturbative QCD predictions and provide inputs for determination of parton density functions. Ratios of jet multiplicities are sensitive to s and have reduced theoretical uncertainties. Measurements of the inclusive isolated-photon and di-photon cross-sections provide a direct probe of short-distance physics, complementary to that from measurements of jets or vector-bosons and are sensitive to the gluon density in the proton. The measurements are compared to next-to-leading-order or higher-order QCD calculationsPeer Reviewe

Calibration and performance of the tile calorimeter of ATLAS with cosmic ray muons

Tese de doutoramento, Física, Universidade de Lisboa, Faculdade de Ciências, 2011The installation of the ATLAS detector in the experimental cavern, took place from 2005 until 2009. During this period, technicians, engineers and physicists have been intensivelyworking on the preparation of the detector for its main objective: probing the new frontiers of high energy physics with the LHC, the particle collider with the largest center of mass energy (14 TeV nominal) and very high luminosities(1034cm−2s−1 nominal). The context of this thesis was this challenging environment that involved all ATLAS members in the preparation of the detector for collisions during the period of the detector commissioning with cosmic ray muons and with calibration and monitoring systems. In 2008 during a short period of time single beam data was available and was used to study the detector response. This large effort was fundamental to prepare the detector for the first collisions at the LHC that started in November 2009. Before collisions started, the only high energy particles available for studieswith the LHC detectors were the muons produced by the interaction of cosmic particles in the atmosphere. These cosmic ray muons are the only detectable particles reaching the earth surface in quantities large enough to study the performance of the different sub-systems of the ATLAS detector. Thework I have developed duringmy PhDand thatwill be detailed in this document is centered on the energy calibration and synchronization of the Tile Calorimeter, the barrel hadronic calorimeter of ATLAS, using cosmic ray muons. The two main topics of study are now summarized: Contribution to the energy calibration of the Tile Calorimeter A electromagnetic energy scale was set in testbeam using high energy particles for 12% of the Tile Calorimeter modules. My contribution was centered in the validation of the global energy scale algorithm and the detector’s energy response uniformity in φ using the TileMuonFitter. The results presented in this document have shown that both the energy scale application, from testbeam to all modules in the experimental cavern, and the energy uniformity in φ are better than 5%. A difference between radial layers A and D of 3% is measured and it is something not completely understood and must be studied later using e.g. isolated muons from collisions. The used data stream and method, still have shown that a full coverage in φ can be achieved for these measurements. These results obtained with an independent method are consistent with an earlier analysis, reported in the readiness paper of the Tile Calorimeter [18]. Calorimeters are not designed and developed for the detection of muons however they play an important role on the commissioning of the LHC detectors and physics program. Before reaching the muon chambers the muons produced in collisions will lose energy in the calorimeter volume. Corrections on the energy loss in the calorimeters are necessary to improve the precision of the muon momentum measurement. This correctionmus be applied to anymuons crossing the calorimeter volume and in particular in fundamental processes used on the final calibration of the detectorwhich includes complex objects as the Z boson decaying to two muons. Lepton isolation techniques are used in the so called golden-channel for the Higgs boson discovery, the decay to four leptons H→ZZ→4l, for the rejection of QCD background. The Tile Calorimeter performance with muons can have an important impact in physics beyond the standard model, such as Super-Symmetry, for instance on the search for stable massive particles, since some of these massive particles are characterized by having an energy loss in the calorimeter similar to muons. The work developed with cosmic muons can also be applied later using muons produced in collisions to monitor the EM scale during the LHC operation. So the work developed with cosmic ray muons is not only important for the commissioning of the detector but can also be relevant for the physics of the LHC to be done with the ATLAS detector. Understanding the response of the Tile Calorimeter to muons as well as to have under control the EM energy scale are fundamental to achieve the best performance of the ATLAS detector. Synchronization of the Tile Calorimeter The Tile Calorimeter synchronization was established during 2008 combining measurements with the laser system and high energy particles: cosmic ray muons and muons from single beam. Thework presented in this thesis uses both types ofmuons, butwith different objectives inmind. Using the single beamdataweremeasured corrections to the velocity of propagation of light in the clear fibers, a parameter used in the laser synchronization. The measured value of 18.5 cm/ns resulted in the update of this parameter in the laser calibration system. The work done with cosmic muons consisted in the determination of the time offsets of the Tile Calorimeter measured both for towers and individual cells. The time offsets were calculated as the residuals after the synchronization made with the laser system. The final results have shown that the cosmic ray muons and single beam data agree within less than 2 ns. The timing is fundamental for the operation of the detector and all systems must be internally synchronized and externally synchronized with the LHC clock ( f = 1 25 ns given by the bunch crossing). The timing plays an important role in the energymeasurement due to the stringent operation conditions of the LHC that require the online signal reconstruction for the Tile Calorimeter channels to be done without iterations. The time of each channel must be known with a precision of the order of a few nanoseconds so that the correct parameters are chosen for the online reconstruction method. Time is also used to select particles that come from p-p collisions, to provide quality factors on the selection of events, and it is the most sensitive quantity for the discovery of slow long lived particles, also called stable massive particles, that are predicted in models beyond the Standard Model. This thesis is divided in 7 chapters. The first is introductory and presents the Large Hadron Collider, the ATLAS detector and its physics goals. In Chapter 2 the Tile Calorimeter is described in some detail presenting the geometry, calibration systems and performance features obtained from the last testbeam results. The following chapters are dedicated to the commissioning of the Tile Calorimeter with cosmic ray muons. The third chapter presents the motivations for the work developed, focusing on the energy scale and synchronization of the Tile Calorimeter. These quantities are of course important in the overall detector performance and have also a larger importance in specific physics channels. Chapter 4 introduces the commissioning and gives a brief overview of the activities during this stage, it is mostly descriptive but also reporting with some detail the activities in which I contributed during the development of my thesis work. The main contributions to the Tile Calorimeter commissioning is included in the next two chapters. Chapter 5 presents the results on the energy scale and uniformity in φ using the TileMuonFitter. Chapter 6 is dedicated to the methods and results for synchronization with cosmic ray muons data. Finally in Chapter 7 conclusions are given.Fundação para a Ciência e Tecnologia (SFRH/BD/27416/2006

Is erucin a promising bioactive against renal cell carcinoma?

A large number of epidemiological studies have linked cruciferous vegetable consumption to a reduced risk of various types of cancer, including renal cell carcinoma. Organosulfur compounds from cruciferous vegetables, glucosinolates and their metabolic breakdown derivatives, isothiocyanates and indole-3-carbinol, rise scientific interest by exerting unique anticancer properties. Erucin (ER) is an isothiocyanate that is generated by enzymatic hydrolyzes of glucoerucin, a glucosinolate predominant found in rocket species, or by in vivo reduction of sulforaphane, its structural oxidized analog. In the present study, the inhibitory effects of ER on renal cancer cell viability, migration and invasion were investigated. The 786- O human renal cancer cell line and the Vero normal-like cells were treated with different concentrations of ER (10-100 μM). Cell viability was determined using the MTT and PI assays. The intracellular level of reactive oxygen species was evaluated using dichlorodihydrofluorescein diacetate. The collective cell migration and chemotaxis/chemoinvasion were studied by a wound healing and transwell assay, respectively. ER induced a concentration-dependent decrease in cell viability, with more cytotoxicity for 786-O cells than against Vero cells. Non-cytotoxic concentration of ER significantly reduced cell migration rate, chemotaxis and invasiveness potential of 786-O cells. The observed favorable anticancer potential of ER against human renal carcinoma in vitro requires further investigation.Nutraceuticals in balancing redox status in ageing and age-related diseases WGs Meeting of the NutRedOx COST Action CA16112 Belgrade, March 2-3, 202

Hadron beam test of a scintillating fibre tracker system for elastic scattering and luminosity measurement in ATLAS

A scintillating fibre tracker is proposed to measure elastic proton scattering at very small angles in the ATLAS experiment at CERN. The tracker will be located in so-called Roman Pot units at a distance of 240 m on each side of the ATLAS interaction point. An initial validation of the design choices was achieved in a beam test at DESY in a relatively low energy electron beam and using slow off-the-shelf electronics. Here we report on the results from a second beam test experiment carried out at CERN, where new detector prototypes were tested in a high energy hadron beam, using the first version of the custom designed front-end electronics. The results show an adequate tracking performance under conditions which are similar to the situation at the LHC. In addition, the alignment method using so-called overlap detectors was studied and shown to have the expected precision.Comment: 12 pages, 8 figures. Submitted to Journal of Instrumentation (JINST

Mechanical construction and installation of the ATLAS tile calorimeter

This paper summarises the mechanical construction andinstallation of the Tile Calorimeter for the ATLASexperiment at the Large Hadron Collider in CERN, Switzerland. The TileCalorimeter is a sampling calorimeter using scintillator as the sensitivedetector and steel as the absorber and covers the central region of the ATLASexperiment up to pseudorapidities ±1.7. The mechanical construction ofthe Tile Calorimeter occurred over a periodof about 10 years beginning in 1995 with the completionof the Technical Design Report and ending in 2006 with the installationof the final module in the ATLAS cavern. Duringthis period approximately 2600 metric tons of steel were transformedinto a laminated structure to form the absorber of the sampling calorimeter.Following instrumentation and testing, which is described elsewhere, themodules were installed in the ATLAS cavern with a remarkable accuracy fora structure of this size and weight.Peer Reviewe

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters