5,531 research outputs found
Inclusive Search for the SM Higgs Boson in the H->gammagamma channel at the LHC
A prospective for the inclusive search of the Standard Model Higgs boson in
the decay channel H->gammagamm is presented with the CMS experiment at the LHC.
The analysis relies on a strategy to determine the background characteristics
and systematics from data. The strategy is applied to a Monte Model of the QCD
background, with full simulation of the detector response. The discrimination
between signal and background exploits information on photon isolation and
kinematics. The resolution for the reconstructed Higgs boson mass profits from
the excellent energy resolution of the CMS crystal calorimeter. A discovery
significance above 5 sigma is expected at integrated LHC luminosities below 30
inverse femtobarn for Higgs boson masses below 140 GeV/c^2.Comment: 7 pages, 3 postscript figues, to appear in the proceedings of the
16th International Conference on Supersymmetry and the Unification of
Fundamental Interactions, Seoul, Korea, June 16-21, 200
Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow
Ion backflow is one of the effects limiting the operation of a gaseous
detector at high flux, by giving rise to space charge which perturbs the
electric field. The natural ability of bulk Micromegas to suppress ion feedback
is very effective and can help the TPC drift volume to remain relatively free
of space charge build-up. An efficient and precise measurement of the backflow
fraction is necessary to cope up with the track distortion due to the space
charge effect. In a subtle but significant modification of the usual approach,
we have made use of two drift meshes in order to measure the ion backflow
fraction for bulk Micromegas detector. This helps to truly represent the
backflow fraction for a TPC. Moreover, attempt is taken to optimize the field
configuration between the drift meshes. In conjunction with the experimental
measurement, Garfield simulation framework has been used to simulate the
related physics processes numerically
An investigation on Vibrionaceae family of bacteria as probiotic factors in shrimp culture
We investigated the effects of Vibrionaceae family of bacteria as probiotics in the process of growth and survival rate of shrimp during propagation stages. Bacterial flora were extracted from seawater, culture farms, shrimp culture farms and sludge of private propagation farms. Different bacteria such as Vibrio alginolyticus (serotype 1-4), Vibrio splendidus I, Vibrio fluvialis II, Vibrio anguillarum I, Vibrio costicul, Vibrio vulnificaus, Vibrio nereis, Vibrio camplbelli, Vibrio natriegens, Vibrio proteolyticus, Vibrio plegius II ,Vibrio fischeri, Aeromonas hydrophila, Aeromonas schuberti, Aeromonas salmonisida, Aeromonas veronii were isolated, identified and lyophilized. These bacteria were used in different experiments on shrimp life cycle stages while the shrimps were being fed on live food such as Chaetoceros, Skeletonema and Tetraselmis algae. Vibrio alginolyticus (serotype 1) with 107 cells/ml increased proliferation of Tetraselmis sp to 71 % in 6 days compared to the control experiment. Also Vibrio alginolyticus (serotype 4) with 105 cells/in' increased Tetraselmis sp. production to 389% in 6 days compared to control. Vibrio splendidus I was also found to be able to increase shrimp fork length in postlarvae stage 3 up to 23% as compared to control. Vibrio alginolyticus and Vibrio fischeri increased survival, fork lenght and body weight of green tiger shrimp in postlarvae stage significantly (P<0.05)
Understanding the reconstruction of personal networks through residential migration trajectories
This article examines how residential trajectories influence the spatiality and composition of personal networks. Three mechanisms are considered: the addition of spatially close network members, the selection of spatially distant network members, and the substitution of spatially distant network members by spatially close ones. An ego-centred network analysis combined with sequence analysis of residential experiences is used to capture the personal networks and the residential trajectories of individuals from two birth cohorts in Switzerland. A series of regression models tests the association between the types of personal networks that individuals develop, in terms of both spatial dispersion and composition, and their residential trajectories. The results show that individuals who moved far away from their place of birth are embedded in large and diversified personal networks, which include spatially distant relatives, local nuclear family members, and local friends. On average, individuals who experienced residential migration have larger and more diverse personal networks than individuals who stayed close to their place of birth. The addition mechanism accounts for much of this greater diversity.</p
Higgs Production and Decay from TeV Scale Black Holes at the LHC
We perform detailed study of the Higgs production and decay, when Higgs is
emitted from the black holes produced in proton-proton collisions at the Large
Hadron Collider. We show that black hole production can significantly enhance
the signal for the Higgs search at the LHC. We evaluate rapidity distribution
of diphotons and transverse momentum distribution of bottom quarks, photons,
tau leptons, top quarks and W bosons from Higgs decay, when Higgs is emitted
from the black hole and also in case when these particles are produced directly
from the black hole evaporation. We compare our results with the standard model
backgrounds. We find that Higgs production from black holes is dominant over
standard model production for GeV, when TeV. Diphotons
from Higgs, when Higgs is produced from evaporation of black holes, are
dominant over the standard model prediction, for diphoton rapidity , while bottom quarks are dominant over QCD background for
large bottom quark transverse momentum, GeV, when TeV. We
show that measurements of the photon and bottom quark transverse momentum
distribution can provide valuable information about the value of the
fundamental Planck scale. We also propose a new signal for black hole
production at the LHC, an onset of increasing transverse momentum distribution
of bottom quarks with large transverse momentum.Comment: 28 pages, 10 figures, 2 tables. Typo corrected; version accepted for
publication in Phys. Rev.
A Time Projection Chamber with GEM-Based Readout
For the International Large Detector concept at the planned International
Linear Collider, the use of time projection chambers (TPC) with micro-pattern
gas detector readout as the main tracking detector is investigated. In this
paper, results from a prototype TPC, placed in a 1 T solenoidal field and read
out with three independent GEM-based readout modules, are reported. The TPC was
exposed to a 6 GeV electron beam at the DESY II synchrotron. The efficiency for
reconstructing hits, the measurement of the drift velocity, the space point
resolution and the control of field inhomogeneities are presented.Comment: 22 pages, 19 figure
Analysing the role of social visits on migrantsâ social capital:A personal network approach
There are concerns that migrants may be embedded in far-flung networks with support being less collective. The spatial dispersion of their relatives and friends would result in fragmented networks with lower solidarity and lower mutual trust than densely connected networks based on geographical proximity. This may be particularly true for migrants who rarely meet their relatives and friends face-to-face. Yet, it is unclear what role, if any, distant visits play in migrantsâ social capital. This article examines these issues using representative data from Switzerland and a combination of network and sequence analysis. Results show that migrants have more spatially dispersed networks, which, in turn, are associated with higher number of emotional support ties compared to respondents with spatially close networks, yet they are characterised by low cohesion and low trust. Distant visits only partly moderate the influence of spatial dispersion on social capital. People who frequently visit or host their far-flung relatives and friends have more transitive networks and fewer supportive ties than those who see them less often, but they do not have higher trust in them. Overall, distant visits have relatively little impact on social capital, suggesting a network effect that goes beyond dyadic relationships
Radiation hardness qualification of PbWO4 scintillation crystals for the CMS Electromagnetic Calorimeter
This is the Pre-print version of the Article. The official published version can be accessed from the link below - Copyright @ 2010 IOPEnsuring the radiation hardness of PbWO4 crystals was one of the main priorities during the construction of the electromagnetic calorimeter of the CMS experiment at CERN. The production on an industrial scale of radiation hard crystals and their certification over a period of several years represented a difficult challenge both for CMS and for the crystal suppliers. The present article reviews the related scientific and technological problems encountered
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