LHC

In this contribution we shall present the results about the physics of the top quark by CERN’s ATLAS and CMS experiments. After a brief motivation of why it is important to study the top quark at the LHC, we shall discuss the measurement of the production cross sections of top pairs and single tops. Then, we shall present an overview its properties: mass, flavour-changing neutral currents (FCNC), anomalous ETmiss, resonances and charge asymmetry. The overall agreement with the Standard Model predictions is very good.

We know little about the mechanisms governing the decline of social movements and the varied forms of individual or collective demobilization that prompt this decline or end it. Yet, the logical counterpart of the initial recruitment and mobilization processes is clearly collective demobilization and individual disengagement. In this paper we start by discussing a plurality of phenomena ranging from individual disengagement to collective demobilization. We then turn to the related questions of the biographical consequences of commitment and of analysis of activist careers in a life-course perspective. We conclude by exploring some avenues for future research.

The production of muons from heavy flavour decays is measured at forward rapidity in proton–proton collisions at s= 7 TeV collected with the ALICE experiment at the LHC. The analysis is carried out on a data sample corresponding to an integrated luminosity Lint= 16.5 nb− 1. The transverse momentum and rapidity differential production cross sections of muons from heavy flavour decays are measured in the rapidity range 2.5

The proposal envisages a new 100km circumference tunnel that would be bored through the Earth, encircling the city of Geneva and the surrounding countryside. [30]
On Wednesday, 25 July, for the very first time, operators injected not just atomic nuclei but lead "atoms" containing a single electron into the LHC. [29]
The case for an ambitious new particle accelerator to be built in the United States has just gotten a major boost.[27]
Physics textbooks might have to be updated now that an international research team has found evidence of an unexpected transition in the structure of atomic nuclei. [26]
The group led by Fabrizio Carbone at EPFL and international colleagues have used ultrafast transmission electron microscopy to take attosecond energy-momentum resolved snapshots (1 attosecond = 10-18 or quintillionths of a second) of a free-electron wave function. [25]

Run 2 of the LHC is generating data that has both a larger volume and a higher complexity, resulting in an increasing requirement for computing resources. LHC Experiments such as ATLAS are thus looking to exploit High Performance Computing as a potential source of computing power, which comes with its own challenges such as limited external connectivity, specialized software stack, and different job submission model. This dissertation focuses on exploring the architecture of HPC systems in contrast to traditional clusters used in Grid computing, and aims to explore the opportunities for performance improvement of ATLAS Simulation jobs when they are run on ARCHER, UK’s National Supercomputing Facility.The dissertation met its primary research objectives through an extensive study of existing literature on ATLAS simulation software and its implementation to HPC, and an elaborate testing process. A performance study was conducted to compare two approaches to running ATLAS jobs on ARCHER. It was found that both approaches had a similar and sub-optimal performance and the total walltime increased almost linearly with an increasing number of nodes on which the simulation was run. The simulation code was optimized using two approaches: the first approach involved minimizing the number of accesses to the filesystem by performing reads and writes on the compute node memory itself, while the second approach involved minimizing simultaneous accesses to the filesystem by delaying the start of the simulation on each node. The optimized simulation code was tested for improvement and no significant improvement in performance was observed. The main conclusion drawn from this study was that the cause for no improvement to be observed was either that the files being moved to compute node memory to minimize filesystem accesses weren’t the correct files required for the simulation, or that the job overlooked the files on the compute node memory and did not read them at all. The dissertation recommended primarily that further investigation is required into tools on ARCHER that would aid in the determination of exactly which files are referenced by a target application, and that a full suite of tests be performed that included tests run using both types of optimizations.

Inclusive DIS type measurements do not constrain the gluon PDF at small x. We study a particular pomeron-like driven exclusive signature involving Heavy Vector Meson (HVM) production that offers increased sensitivity to the PDF in precisely this domain. The previously known photoproduction amplitude is considered in the first instance to NLO, where the method of calculation and tool chain employed therein is described and is amenable to extension to the more general case of electroproduction. We end with a brief outlook into how one can start to include small x experimental data into the global fitter PDF analyses.

Mass coral bleaching events are a worldwide phenomenon, which generally occur during periods of elevated sea surface temperature and intense sunlight. These conditions result in a decline in photochemical efficiency of symbiotic microalgae (zooxanthellae) which ultimately leads to the expulsion of these symbionts. The physiological mechanism which triggers the release of the zooxanthellae has yet to be adequately determined. Under bleaching conditions, non-photochemical quenching (NPQ) is used to dissipate excess energy from photosystem II (PSII). NPQ was partitioned into three components, (energy dependent quenching [qE], state transition quenching [qT] and photoinhibitory quenching [qI]), based on relaxation kinetics upon addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and darkening. This investigation revealed that for corals not exposed to bleaching stress, qE was the principle means of energy dissipation (∼60% of the total NPQ). In corals exposed to either high-light (475 μmol photons m−2 s−1 and 25 °C) or elevated temperature (225 μmol photons m−2 s−1 and 32 °C) treatments, the dominant component of NPQ was qE and the relative proportions did not change during the exposure period (1–8 h). When exposed to bleaching conditions (475 μmol photons m−2 s−1 and 32 °C) the contribution of the different components changed after 4 h and the total NPQ increased. At this time, the contribution of qT to the total NPQ significantly increased to equal that of qE (40%), suggesting state transitions become more important under such conditions. Throughout the exposure period in all treatments, no change in the proportion of qI was observed.

We discuss a possible staged upgrade of the LHC and of its injectors, with a view to increasing the luminosity from the nominal 10** 34 cm**-2s**-1 to 10** 35 cm**-2s**-1 in each of the two high-luminosity experiments. We also consider possible scenarios for an ...

FLUKA is a general purpose Monte Carlo code capable of handling all radiation components from thermal energies (for neutrons) or 1keV (for all other particles) to cosmic ray energies and can be applied in many different fields. Presently the code is maintained on Linux. The validity of the physical models implemented in FLUKA has been benchmarked against a variety of

Trypsin-induced effects on the PSI-photochemical activity of pea chloroplast membranes have been measured under saturating light conditions. It was found that incubation of isolated chloroplasts with ttypsin in concentration range of 20-60 pg trypsin per mg Chl leads to a linear increase of the rate of PSI-mediated electron transport, measured by 01-uptake with methyl viologen as an electron acceptor and DCPIP-H, as electron donor. Low temperature (77 K) chlorophyll fluorescence measurements have indicated that a remarkable redistribution of excitation light energy in favor of PSI occurs under these conditions. The results are interpreted in terms of trypsin-induced lateral reorganization of the chlorophyll-protein complexes within the thylakoid membranes and specific alteration at the level of LHC a /b-PSI1 supramolecular organization.

The heaviest known elementary particle, the top quark, was discovered in 1995 by the CDF and D0 collaborations at the Tevatron proton–antiproton collider at Fermilab. Since its discovery, a large program was set in motion by the CDF and D0 collaborations to characterize the production and decay properties of top quarks, and investigate their potential for searches of new phenomena beyond the standard model. During the past 20 years, new methods were developed and implemented to improve the measurements and searches for new physics in the top quark sector. This paper reviews the achievements and results obtained through studies of the top quark at the Tevatron.

We know little about the mechanisms governing the decline of social movements and the varied forms of individual or collective demobilization that prompt this decline or end it. Yet, the logical counterpart of the initial recruitment and mobilization processes is clearly collective demobilization and individual disengagement. In this paper we start by discussing a plurality of phenomena ranging from individual disengagement to collective demobilization. We then turn to the related questions of the biographical consequences of commitment and of analysis of activist careers in a life-course perspective. We conclude by exploring some avenues for future research.

In this contribution we shall present the results about the physics of the top quark by CERN’s ATLAS and CMS experiments. After a brief motivation of why it is important to study the top quark at the LHC, we shall discuss the measurement of the production cross sections of top pairs and single tops. Then, we shall present an overview its properties: mass, flavour-changing neutral currents (FCNC), anomalous ETmiss, resonances and charge asymmetry. The overall agreement with the Standard Model predictions is very good.

We discuss a possible staged upgrade of the LHC and of its injectors, with a view to increasing the luminosity from the nominal 10** 34 cm**-2s**-1 to 10** 35 cm**-2s**-1 in each of the two high-luminosity experiments. We also consider possible scenarios for an ...

Among the mechanisms which successfully explain the generation of the Baryon Asymmetry of the Universe, Leptogenesis through right-handed neutrino decays is especially attractive. Unfortunately, this theory suffers from a lack of testability. Indeed, the high energy relevant ingredients in the asymmetry creation are either indirectly linked to low energy observables or unreachable by our present experiments. We propose here to take the problem the other way around by studying whether this mechanism could at least be disproved. We argue that the observation of a right handed gauge boson W_R at future colliders could play this role.