145 research outputs found
Top-quark Polarization and Asymmetries at the LHC in the Effective Description of Squark Interactions
A detailed study of top-quark polarizations and charge
asymmetries, induced by top-squark-pair production at the LHC and the
subsequent decays , is performed within the
effective description of squark interactions, which includes the effective
Yukawa couplings and another logarithmic term encoding the supersymmetry
breaking. This effective approach is more suitable for its introduction into
Monte-Carlo simulations and we make use of its implementation in {\tt MadGraph}
in order to investigate the possibilities of the charge asymmetry ,
measured at the LHC and consistent with SM expectations, to discriminate among
different SUSY scenarios and analyze the implications of these scenarios in the
top polarizations and related observables.Comment: LaTeX file. 27 pages, 6 figures, 10 tables: v3 matches published
manuscript Eur.Phys.J. C75 (2015) 1, 3
Risk factors for African swine fever incursion in Romanian domestic farms during 2019
African swine fever (ASF) entered Georgia in 2007 and the EU in 2014. In the EU, the virus primarily spread in wild boar (Sus scrofa) in the period from 2014–2018. However, from the summer 2018, numerous domestic pig farms in Romania were affected by ASF. In contrast to the existing knowledge on ASF transmission routes, the understanding of risk factors and the importance of different transmission routes is still limited. In the period from May to September 2019, 655 Romanian pig farms were included in a matched case-control study investigating possible risk factors for ASF incursion in commercial and backyard pig farms. The results showed that close proximity to outbreaks in domestic farms was a risk factor in commercial as well as backyard farms. Furthermore, in backyard farms, herd size, wild boar abundance around the farm, number of domestic outbreaks within 2 km around farms, short distance to wild boar cases and visits of professionals working on farms were statistically significant risk factors. Additionally, growing crops around the farm, which could potentially attract wild boar, and feeding forage from ASF affected areas to the pigs were risk factors for ASF incursion in backyard farms.We acknowledge financial support from EFSA, ANSVSA and from the Danish Veterinary and Food Administration (FVST) as part of the agreement of commissioned work between the Danish Ministry of Food, Agriculture and Fisheries and the University of Copenhagen.Peer reviewe
Strange particle production in proton-proton collisions at TeV with ALICE at the LHC
The production of mesons containing strange quarks (K, ) and both
singly and doubly strange baryons (, Anti-, and
+Anti-) are measured at central rapidity in pp collisions at
= 0.9 TeV with the ALICE experiment at the LHC. The results are
obtained from the analysis of about 250 k minimum bias events recorded in 2009.
Measurements of yields (dN/dy) and transverse momentum spectra at central
rapidities for inelastic pp collisions are presented. For mesons, we report
yields () of 0.184 0.002 stat. 0.006 syst. for K and
0.021 0.004 stat. 0.003 syst. for . For baryons, we find
= 0.048 0.001 stat. 0.004 syst. for , 0.047
0.002 stat. 0.005 syst. for Anti- and 0.0101 0.0020 stat.
0.0009 syst. for +Anti-. The results are also compared with
predictions for identified particle spectra from QCD-inspired models and
provide a baseline for comparisons with both future pp measurements at higher
energies and heavy-ion collisions.Comment: 33 pages, 21 captioned figures, 10 tables, authors from page 28,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Transverse momentum spectra of charged particles in proton-proton collisions at GeV with ALICE at the LHC
The inclusive charged particle transverse momentum distribution is measured
in proton-proton collisions at GeV at the LHC using the ALICE
detector. The measurement is performed in the central pseudorapidity region
over the transverse momentum range GeV/.
The correlation between transverse momentum and particle multiplicity is also
studied. Results are presented for inelastic (INEL) and non-single-diffractive
(NSD) events. The average transverse momentum for is (stat.) (syst.) GeV/ and
\left_{\rm NSD}=0.489\pm0.001 (stat.) (syst.)
GeV/, respectively. The data exhibit a slightly larger than measurements in wider pseudorapidity intervals. The results are
compared to simulations with the Monte Carlo event generators PYTHIA and
PHOJET.Comment: 20 pages, 8 figures, 2 tables, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/390
Production of pions, kaons and protons in pp collisions at GeV with ALICE at the LHC
The production of , , , , p, and pbar at mid-rapidity
has been measured in proton-proton collisions at GeV with the
ALICE detector. Particle identification is performed using the specific energy
loss in the inner tracking silicon detector and the time projection chamber. In
addition, time-of-flight information is used to identify hadrons at higher
momenta. Finally, the distinctive kink topology of the weak decay of charged
kaons is used for an alternative measurement of the kaon transverse momentum
() spectra. Since these various particle identification tools give
the best separation capabilities over different momentum ranges, the results
are combined to extract spectra from = 100 MeV/ to 2.5 GeV/.
The measured spectra are further compared with QCD-inspired models which yield
a poor description. The total yields and the mean are compared with
previous measurements, and the trends as a function of collision energy are
discussed.Comment: 24 pages, 18 captioned figures, 5 tables, published version, figures
at http://aliceinfo.cern.ch/ArtSubmission/node/388
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