2,817 research outputs found
Results on Diffraction at HERA and Tevatron
Recent results on diffraction at HERA, from the H1 and ZEUS Collaborations,
and at Tevatron, from the CDF and D0 Collaborations, are reviewed. The
measurement of the diffractive structure function at HERA is presented, and the
pomeron structure function is extracted from QCD fits. Diffractive dijet
production is given as an example analysis of the diffractive final state.
These analysis are consistent with a leading gluon partonic structure for the
pomeron. Hard single diffraction, double diffraction and double pomeron
exchange processes are studied at the Tevatron and complement the studies
performed at HERA. Finally, HERA results on the diffractive (exclusive)
production of a vector particle, either a vector meson or a photon, are
presented and compared to models based on perturbative QCD.Comment: Results presented at "La Thuile" conference, feb/mar 2000, Italy. To
appear in the proceedings. 12 pages, 10 figure
Elastic production of Vector Mesons at HERA: study of the scale of the interaction and measurement of the helicity amplitudes
A compilation of H1 and ZEUS cross section measurements for elastic vector
meson production is presented as a function of the scale ,
where Q^2 is the exchanged photon virtuality and M_V is the mass of the vector
meson. The ratio of longitudinal to transverse cross sections R =
is presented as a function of Q^2/M^2_V. The cross sections
are separated in a transverse and a longitudinal component, and are presented
as a function of K^2. The intercept -- 1 governing the energy
dependence of the vector meson cross sections is compared with the
parameter measured in inclusive F_2 analysis. For meson production, the
helicity amplitude ratios , extracted from the H1 and ZEUS
measurements of the spin density matrix elements are presented as a function of
Q^2 and W and are compared to recent predictions.Comment: The note includes plots presented in the vector meson discussion
session of the Workshop of Low-x Physics (june 1999), Tel-Aviv, Israel. 12
pages, 7 figures, 1 table. New version with new model predictio
Search with the CMS detector for heavy resonances decaying into an electron pair
This note presents the CMS experiment potential to discover heavy resonances decaying into an electron-positron pair, such as Kaluza-Klein excitations of a Z or graviton boson predicted in extra dimension models (the TeV^-1 model and the Randall-Sundrum model), or as neutral heavy Z' boson predicted by Grand Unified Theories. Full and fast simulation and reconstruction are used to investigate these productions, with the pileup condition corresponding to a luminosity equal to 2 times 10^ 33; mathrm cm ^ -2 mathrm s ^ -1 . For an integrated luminosity of 60 fbinv, a 5 sigma discovery limit has been obtained for a mass of 5.9 tevct in the case of Kaluza-Klein excitation Z boson production. For the Randall-Sundrum graviton production, the limit is found for graviton masses of 1.8 tevct with a coupling parameter constant c=0.01 and 4.1 tevct for c=0.1 . For the six Z' models considered here, the 5 sigma discovery limit ranges for masses from 3.6 tevct (rm Z_psi) to 4.6 tevct (rm Z_ALRM)
Model-independent constraints on the CKM matrix elements , and
Single top quark production cross sections at hadron colliders are
traditionally used to extract the modulus of the element of the
Cabibbo-Kobayashi-Maskawa matrix under the following assumption: . For the first time, direct limits on and
are obtained using experimental data without the assumption of the
unitarity of the CKM matrix. Limits on the , and
are extracted from differential measurements of single top quark
cross sections in -channel as a function of the rapidity and transverse
momentum of the top quark and the light jet recoiling against the top quark. We
have shown that the pseudorapidity of the forward jet in the single top
production is one of the most powerful observables for discriminating between
the and events. We perform a global fit of top quark
related CKM elements to experimental data from the LHC Runs I and II and
Tevatron. Experimental data include inclusive and differential single top cross
sections in -channel, inclusive tW production cross section, and top quark
branching ratio to b quark and W boson. We present bounds on ,
and using current data and project the results for future
LHC data sets corresponding to luminosities of 300 and 3000 \fb
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TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
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