2,827 research outputs found
Impact of future HERA data on the determination of proton parton distribution functions using the ZEUS QCD fit
The high precision and large kinematic coverage of the data from the HERA-I
running period (1994-2000) have already allowed precise extractions of proton
parton distribution functions (PDFs). The HERA-II running program is now
underway and is expected to provide a substantial increase in the luminosity
collected at HERA. In this paper, a study is presented which investigates the
potential impact of future data from HERA on the proton PDF uncertainties,
within the currently planned running scenario. In addition, the effect of a
possible future measurement of the longitudinal structure function, FL, on the
gluon distribution is investigated.Comment: 5 pages, 2 figures, in proceedings of the XIII International Workshop
on Deep Inelastic Scattering - DIS 2005, Madison, Wisconsin, 200
Chemical Differentiation toward the Pipe Nebula Starless Cores
We used the new IRAM 30-m FTS backend to perform an unbiased ~15 GHz wide
survey at 3 mm toward the Pipe Nebula young diffuse starless cores. We found an
unexpectedly rich chemistry. We propose a new observational classification
based on the 3 mm molecular line emission normalized by the core visual
extinction (Av). Based on this classification, we report a clear
differentiation in terms of chemical composition and of line emission
properties, which served to define three molecular core groups. The "diffuse"
cores, Av<~15, show poor chemistry with mainly simple species (e.g. CS and
CCH). The "oxo-sulfurated" cores, Av~15--22, appear to be abundant in species
like SO and SO2, but also in HCO, which seem to disappear at higher densities.
Finally, the "deuterated" cores, Av>~22, show typical evolved chemistry prior
to the onset of the star formation process, with nitrogenated and deuterated
species, as well as carbon chain molecules. Based on these categories, one of
the "diffuse" cores (Core 47) has the spectral line properties of the
"oxo-sulfurated" ones, which suggests that it is a possible failed core.Comment: Accepted for publication in A&A. 5 pages, 2 figure
A comment on "Amplification of endpoint structure for new particle mass measurement at the LHC"
We present a comment on the kinematic variable recently proposed in
"Amplification of endpoint structure for new particle mass measurement at the
LHC". The variable is designed to be applied to models such as R-parity
conserving Supersymmetry (SUSY) when there is pair production of new heavy
particles each of which decays to a single massless visible and a massive
invisible component. It was proposed in "Amplification of endpoint structure
for new particle mass measurement at the LHC" that a measurement of the peak of
the distribution could be used to precisely constrain the masses of
the SUSY particles. We show that when Standard Model backgrounds are included
in simulations, the sensitivity of the variable to the SUSY particle
masses is more seriously impacted for than for other previously
proposed variables.Comment: 5 page
Mass measurement in boosted decay systems at hadron colliders
We report a new possibility of using the \mct2 (Constransverse mass)
variable for mass measurement in single step decay chains involving missing
particles with moderate transverse momentum. We show that its experimental
feasibility is enhanced compared to the corresponding \mt2-kink method. We
apply this method to reconstruct a pair of chargino decay chains.Comment: 6 pages, 12 figures, published in PRD,
http://link.aps.org/doi/10.1103/PhysRevD.84.03501
Summary of the Topical Workshop on Top Quark Differential Distributions 2014
We summarise the Topical Workshop on Top Quark Differential Distributions
2014, which took place in Cannes immediately before the annual Top2014
conference. The workshop was motivated by the availability of top quark
differential distributions at NNLO and the forthcoming LHC 13 TeV data. The
main goal of the workshop was to explore the impact of improved calculations of
top quark production on precision LHC measurements, PDF determinations and
searches for physics beyond the Standard Model, as well as finding ways in
which the high precision data from ATLAS, CMS and LHCb can be used to further
refine theoretical predictions for top production.Comment: 9 pages, 5 figures, proceedings of TOP2014, 7th International
Workshop on Top-Quark Physics, Cannes, Franc
The stransverse mass, MT2, in special cases
This document describes some special cases in which the stransverse mass,
MT2, may be calculated by non-iterative algorithms. The most notable special
case is that in which the visible particles and the hypothesised invisible
particles are massless -- a situation relevant to its current usage in the
Large Hadron Collider as a discovery variable, and a situation for which no
analytic answer was previously known. We also derive an expression for MT2 in
another set of new (though arguably less interesting) special cases in which
the missing transverse momentum must point parallel or anti parallel to the
visible momentum sum. In addition, we find new derivations for already known
MT2 solutions in a manner that maintains manifest contralinear boost invariance
throughout, providing new insights into old results. Along the way, we stumble
across some unexpected results and make conjectures relating to geometric forms
of M_eff and H_T and their relationship to MT2.Comment: 11 pages, no figures. v2 corrects minor typos. v3 corrects an
incorrect statement in footnote 8 and inserts a missing term in eq (3.9). v4
and v5 correct minor typos spotted by reader
- …