Studying WWγWW\gamma and WZγWZ\gamma production in proton-proton collisions at s=8\sqrt{s} = 8 TeV with the ATLAS experiment

Quartic gauge couplings are tested by this study of the production of $WW\gamma$ and $WZ\gamma$ events in 20.2 fb$^{-1}$ of proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV recorded with the ATLAS detector at the LHC. The final state of $WW\gamma$ events containing an electron, a muon and a photon is analysed as well as the final states of $WW\gamma$ and $WZ\gamma$ production containing an electron or a muon, two jets and a photon. For all final states two different fiducial regions are defined: one yielding the best sensitivity to the production cross-section of the process and one optimised for the detection of new physical phenomena. In the former region, the $WW\gamma$ production cross-section is computed and in both regions, upper limits on the $WW\gamma$ and $WZ\gamma$ production cross-section are derived. The results obtained in the second phase space are combined for the interpretation in the context of anomalous quartic gauge couplings using an effective field theory.Comment: Proceedings of the Fifth AnnualLHC

Inverse Compton emission from heavy WIMP annihilations in the Galactic Centre

A thermal relic WIMP remains a prime candidate for the nature of Dark Matter,particularly for the more poorly constrained case of a heavy ($\gtrsim$ 1 TeV)WIMP. The highest fluxes from WIMP annihilations are expected in the region ofthe Galactic Centre (GC) where current and near future gamma-ray observatoriescan be exploited to place tight limits on the WIMP paradigm. It is regularlynoted that the annihilation flux of gammas will be accompanied by chargedsecondary particles which can produce 'delayed' inverse Compton (IC) gamma-rayemission, but this component is often neglected in indirect Dark Mattersearches. In this work the inverse Compton emission is studied for the specificconditions of heavy WIMP annihilation in the GC. Using models for the magneticand radiation fields of the region, and taking into consideration the transportof secondary particles, we find that for TeV WIMPs the IC component cannot beneglected in the GC, with the particles produced cooling within the regionrather than propagating out in to the Galaxy. This effect changes the predictedspectral shape substantially and thus boosts the detection prospects for heavyWIMPs.<br

Sammenligning av interferens på sekundæroppgaver i proksimale versus distale effektorer i arm

Formålet med dette studiet var å studere proksimal og distal muskulatur i ulike dual-task regimer, hvor man skal kontrollere en primæroppgave, og se hvor mye en sekundæroppgave interfererer. Primæroppgaven bestod av å kontrollere en joystick med proksimale eller distale effektorer i dominant arm. Sekundæroppgavene var i en kondisjon en motorisk oppgave på non-dominant arm, og i den andre en kognitiv sekundæroppgave som gikk ut på å stave ord baklengs. Det teoretiske grunnlaget for dette studiet er basert på nevroanatomiske og nevrofysiologiske forskjeller mellom proksimal og distal muskulatur. Fjorten forsøkspersoner deltok i studiet, hvor de dag en hadde tilvenning av primæroppgaven med både proksimal og distal joystick. Dag to, test-dagen, ble de ulike kondisjonene gjennomført med et A-B-A-C-A-design. Det ble funnet ingen signifikant forskjell i nedgangen av prestasjonen på primæroppgaven kontrollert av proksimal eller distal muskulatur når man samtidig utførte den kognitive sekundæroppgaven. Det ser ut som at de ulike kortikospinale banene ikke påvirker den motoriske primæroppgaven ved en kognitiv sekundæroppgave. Derimot ble det funnet en signifikant forskjell i nedgang av prestasjon på primæroppgaven mellom proksimale og distale effektorer, når man samtidig utfører en motorisk sekundæroppgave. At proksimal muskulatur interfereres i større grad av den motoriske sekundæroppgaven kan forklares ut i fra større bilaterale forbindelser for proksimal muskulatur sammenlignet med distal muskulatur. The purpose of the present study was to study proximal and distal musculature in different dual-task regimes, in form of controlling a primary-task, and see how much a secondary-task interference. The primary-task consisted of controlling a joystick with proximal or distal effectors in dominant arm. The secondary-task was respectively in one condition a motor task in non-dominant arm, and a cognitive task consisting of spelling words backwards. The theoretical framework for this study is derived from neuroanatomical and neurophysiological differences to proximal and distal muscles. Fourteen subjects participated in the study, where the first day was habituation of the primary-task with both proximal and distal joystick. The second day, the test day, the different conditions were completed with an A-B-A-C-A-design. It was found no significant differences in performance decline between a primary-task controlled of proximal or distal muscles while handling a cognitive secondary-task. It seems like the different corticospinal pathway did not affect the motor primary-task while handling a cognitive secondary-task. However, it was a significant difference in decline in performance between proximal and distal effectors on the primary-task, when handling a motor secondarytask simultaneously. Proximal muscles interference more with a motor secondary-task could be explained by greater bilateral interactions for proximal muscles than distal muscles

Analysis of WWγ production with the ATLAS experiment

In this thesis, triboson final states containing two W bosons and a photon are studied using proton-proton collisions. The data set was recorded with the ATLAS detector at a centre-of-mass energy of √s = 8 TeV and corresponds to an integrated luminosity of 20.3 fb⁻¹. The fiducial cross-section of the process W W γ → eνμνγ is measured for the first time in hadron collisions and corresponds to σ = (1.89 ± 0.93(stat.) ± 0.41(syst.) ± 0.05(lumi.)) fb. It is in good agreement with the Standard Model prediction at next-to-leading order in the strong coupling constant. As no deviation from the Standard Model expectation is observed, frequentist limits at 95 % confidence level are computed to exclude contributions from anomalous quartic gauge couplings. This analysis is sensitive to fourteen coupling parameters of mass dimension eight and the limits are derived for all parameters with and without unitarisation

More pronounced bimanual interference in proximal compared to distal effectors of the upper extremities

Bimanual performance depends on effective and modular bilateral communication between the two bodysides. Bilateral neural interactions between the bodysides could cause bimanual interference, and the neuromuscular system for proximal and distal muscles is differently organized, where proximal muscles have more bilateral interneurons at both cortical and spinal level compared to distal muscles. These differences might increase the potential for bimanual interference between proximal arm muscles, because of greater proportions of bilateral interneurons to proximal muscles. The purpose of the present experiment was to evaluate potential differences in bimanual interference between proximal versus distal effectors in the upper extremities. 14 participants first performed a unilateral primary motor task with dominant arm with (1) a proximal and (2) distal controlled joysticks (condition A). Performance in condition A, was compared with the same effector’s performance when a bimanual interference task was performed simultaneously with the non-dominant arm (condition B). The results showed a significant bimanual interference for both the proximal and distal controlled joysticks. Most interestingly, the bimanual interference was larger for the proximal joystick compared to the distal controlled joystick. The increase in spatial accuracy error was higher for the proximal controlled joystick, compared with the distal controlled joystick. These results indicate that the proximal-distal distinction is an important organismic constraint on motor control, and especially for bilateral communication. There seem to be an undesired bilateral interference for both proximal and distal muscles. The interference is higher in the case of proximal effectors compared distal effectors, and the results seem to map the neuroanatomical and neurophysiological differences for these effectors.publishedVersio

Bulk Properties of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV measured by ALICE

Global variables, such as the charged particle multiplicity and the transverse energy are important observables to characterize Relativistic Heavy Ion collisions and to constrain model calculations. The charged particle multiplicity dNch/deta and transverse energy dET/deta are measured at sqrt(sNN) = 2.76 TeV in Pb-Pb collisions as a function of centrality and in pp collisions. The fraction of inelastic cross section seen by the ALICE detector is calculated either using a Glauber model or the data corrected by simulations of nuclear and electromagnetic processes, or data collected with a minimum bias interaction trigger. The centrality, defined by the number of nucleons participating in the collision, is obtained, via the Glauber model, by relating the multiplicity distributions of various detectors in the ALICE Central Barrel and their correlation with the spectator energy measured by the Zero-Degree Calorimeters. The results are compared to corresponding results obtained at the significantly lower energies of the BNL AGS, the CERN SPS, and the BNL RHIC, and with models based on different mechanisms for particle production in nuclear collisions. Particular emphasis will be given to a discussion on systematic studies of the dependence of the centrality determination on the details of the Glauber model, and the validity of the Glauber model at unprecedented collision energies.Comment: Proceedings of the XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collisions Quark Matter 2011, submitted to J. Phys. G: Nucl. Part. Phys. 8 pages, 7 (multi)figure

Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at sNN\sqrt{s_{NN}} = 5.02 TeV

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7 $< p_{\rm{T}, assoc} < p_{\rm{T}, trig} <$ 5.0 GeV/$c$ is examined, to include correlations induced by jets originating from low momen\-tum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta|<0.9$. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton--parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/161

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}}=2.76 TeV

The elliptic, $v_2$, triangular, $v_3$, and quadrangular, $v_4$, azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions and (anti-)protons in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range $|\eta|<0.8$ at different collision centralities and as a function of transverse momentum, $p_{\rm T}$, out to $p_{\rm T}=20$ GeV/$c$. The observed non-zero elliptic and triangular flow depends only weakly on transverse momentum for $p_{\rm T}>8$ GeV/$c$. The small $p_{\rm T}$ dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to $p_{\rm T}=8$ GeV/$c$. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least $p_{\rm T}=8$ GeV/$c$ indicating that the particle type dependence persists out to high $p_{\rm T}$.Comment: 16 pages, 5 captioned figures, authors from page 11, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186

Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm{NN}}} = 2.76 TeV

The inclusive transverse momentum ($p_{\rm T}$) distributions of primary charged particles are measured in the pseudo-rapidity range $|\eta|<0.8$ as a function of event centrality in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=2.76$ TeV with ALICE at the LHC. The data are presented in the $p_{\rm T}$ range $0.15<p_{\rm T}<50$ GeV/$c$ for nine centrality intervals from 70-80% to 0-5%. The Pb-Pb spectra are presented in terms of the nuclear modification factor $R_{\rm{AA}}$ using a pp reference spectrum measured at the same collision energy. We observe that the suppression of high-$p_{\rm T}$ particles strongly depends on event centrality. In central collisions (0-5%) the yield is most suppressed with $R_{\rm{AA}}\approx0.13$ at $p_{\rm T}=6$-7 GeV/$c$. Above $p_{\rm T}=7$ GeV/$c$, there is a significant rise in the nuclear modification factor, which reaches $R_{\rm{AA}} \approx0.4$ for $p_{\rm T}>30$ GeV/$c$. In peripheral collisions (70-80%), the suppression is weaker with $R_{\rm{AA}} \approx 0.7$ almost independently of $p_{\rm T}$. The measured nuclear modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/284