942 research outputs found
Particle and Nuclear Physics with High Energy Leptons
In high centre-of-mass energy lepton-nucleon collisions the space-time time
resolution of partonic processes can be {\it fine-tuned} within a dynamical
range which is unattainable in hadronic collisions. Replacing nucleons by
nuclei of variable atomic number enables one to tune the strength of colour
forces. The experimental program of high energy electron-nucleon and its
extension to electron-nucleus collisions should thus give an unique opportunity
to experimentally explore the transition between the soft and hard interactions
of small and extended partonic systems. Such an experimental program, which can
be realized at DESY and/or BNL with relatively modest cost, is discussed in
this talk.Comment: Plenary talk at the PANIC conference, Uppsala, June 1999. 8 pages. 3
figure
The measurement of the W mass at the LHC: shortcuts revisited
The claim that the W mass will be measured at the LHC with a precision of (10)~MeV is critically reviewed. It is argued that in order to achieve such precision, a considerably better knowledge of the , , , , and structure functions of the proton than available today is needed. This will permit to assess with adequate precision the production characteristics of the W and Z bosons in the proton--proton collisions at the LHC, and their effect on the spectra of charged leptons from W and Z decays. An experimental programme is suggested that will deliver the missing information. The core of this programme is a dedicated muon scattering experiment at the CERN SPS, with simultaneous measurements on hydrogen and deuterium targets
Large Extra Dimension effects through Light-by-Light Scattering at the CERN LHC
Observing light-by-light scattering at the Large Hadron Collider (LHC) has
received quite some attention and it is believed to be a clean and sensitive
channel to possible new physics. In this paper, we study the diphoton
production at the LHC via the process through graviton exchange in the Large Extra
Dimension (LED) model. Typically, when we do the background analysis, we also
study the Double Pomeron Exchange (DPE) of production. We
compare its production in the quark-quark collision mode to the gluon-gluon
collision mode and find that contributions from the gluon-gluon collision mode
are comparable to the quark-quark one. Our result shows, for extra dimension
, with an integrated luminosity at the
14 TeV LHC, that diphoton production through graviton exchange can probe the
LED effects up to the scale for the forward
detector acceptance , respectively, where
, and .Comment: 25 pages. 7 figs. Change some grammatical error
Cross Section Ratios between different CM energies at the LHC: opportunities for precision measurements and BSM sensitivity
The staged increase of the LHC beam energy provides a new class of
interesting observables, namely ratios and double ratios of cross sections of
various hard processes. The large degree of correlation of theoretical
systematics in the cross section calculations at different energies leads to
highly precise predictions for such ratios. We present in this letter few
examples of such ratios, and discuss their possible implications, both in terms
of opportunities for precision measurements and in terms of sensitivity to
Beyond the Standard Model dynamics.Comment: 19 pages, 9 figure
Theoretical Uncertainties in Electroweak Boson Production Cross Sections at 7, 10, and 14 TeV at the LHC
We present an updated study of the systematic errors in the measurements of
the electroweak boson cross-sections at the LHC for various experimental cuts
for a center of mass energy of 7, 10 and 14 TeV. The size of both electroweak
and NNLO QCD contributions are estimated, together with the systematic error
from the parton distributions. The effects of new versions of the MSTW, CTEQ,
and NNPDF PDFs are considered.Comment: PDFLatex with JHEP3.cls. 22 pages, 43 figures. Version 2 adds the
CT10W PDF set to analysis and updates the final systematic error table and
conclusions, plus several citations and minor wording changes. Version 3 adds
some references on electroweak and mixed QED/QCD corrections. Version 4 adds
more references and acknowledgement
Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s
A precise measurement of the inclusive deep-inelastic e^+p scattering cross
section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and
3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in
1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The
double differential cross section, from which the proton structure function
F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is
measured with typically 1% statistical and 3% systematic uncertainties. The
measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise
continuously towards small x for fixed Q^2. The cross section data are combined
with published H1 measurements at high Q^2 for a next-to-leading order DGLAP
QCD analysis.The H1 data determine the gluon momentum distribution in the range
3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20
GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS
collaboration allows the strong coupling constant alpha_s and the gluon
distribution to be simultaneously determined. A value of alpha
_s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with
an additional theoretical uncertainty of about +-0.005, mainly due to the
uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
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