Measurements of Diffractive Vector-Meson Photoproduction at High Momentum Transfer from the ZEUS Experiment at HERA

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 187-189
Author(s):  
James A. Crittendenr
Keyword(s):  
Momentum Transfer ◽  
Cross Sections ◽  
Zeus Collaboration ◽  
Center Of Mass ◽  
High Momentum ◽  
Mass Energy ◽  
Meson Photoproduction ◽  
High Momentum Transfer ◽  
Center Of Mass Energy ◽  
Dissociated State

We discuss recent preliminary results on the diffractive photoproduction of ρ0, ϕ, and J/ψ mesons at high momentum transfer reported by the ZEUS collaboration at HERA. A special-purpose calorimeter served to tag the quasi-real photons (Q2<0.01 GeV 2) in the process γ+p→ VM +Y, where Y represents a dissociated state of the proton. The resulting range in photon-proton center-of-mass energy extends from 80 to 120 GeV. The differential cross sections [Formula: see text] were obtained in the region |t| > 1.2 GeV 2, where t denotes the squared momentum transfer to the proton. The measurements provide good sensitivity to the observed power-law dependence [Formula: see text]. Over the region in momentum transfer covered by the data, the power is found to be approximately n ≃ 3 for ρ0 and ϕ photoproduction, and approximately n ≃ 2 for J/ψ photoproduction.

scholarly journals Non-strange dibaryons studied in coherent double neutral-meson photoproduction on the deuteron

2020 ◽  
Vol 241 ◽  
pp. 01007
Author(s):  
Takatsugu Ishikawa ◽  
Hisako Fujimura ◽  
Hiroshi Fukasawa ◽  
Ryo Hashimoto ◽  
Qinghua He ◽  
...  
Keyword(s):  
Invariant Mass Distribution ◽  
Center Of Mass ◽  
Resonance State ◽  
Angular Distributions ◽  
Neutral Meson ◽  
Mass Energy ◽  
Meson Photoproduction ◽  
Neutral Pions ◽  
Center Of Mass Energy ◽  
Interesting Object

The B = 2 bound/resonance state (dibaryon) is an interesting object, which can be a molecule consisting of two baryons or a spatially compact hexaquark hadron object. The yd ^ n°n°d reaction has been experimentally investigated at incident energies ranging from 0.58 to 1.15 GeV to study non-strange dibaryons. The angular distributions of deuteron emission in the yd center-of-mass energy cannot be reproduced by quasi-free production of two neutral pions followed by deuteron coalescence. Additionally a 2.14-GeV peak is observed in the n°d invariant mass distribution. These suggest a sequential process such as yd ^ RIS ^ n°RIV ^ n°n°d with an isoscalar dibaryon RIS and an isovector dibaryon RIV. Since the mass of the observed isoscalar dibaryons are close to the sum of the nucleon (N) and nucleon resonance (N*) masses, an S-wave NN* molecule may play a role as a doorway to a dibaryon.

scholarly journals New Fitting Concept in ATLAS muon tracking for the LHC Run-2

2019 ◽  
Vol 214 ◽  
pp. 06006
Author(s):  
William Leight ◽  
Pierre-Francois Giraud ◽  
Peter Kluit ◽  
Jochen Meyer ◽  
Edward Moyse ◽  
...  
Keyword(s):  
Center Of Mass ◽  
New Physics ◽  
High Momentum ◽  
Alignment Quality ◽  
Mass Energy ◽  
Center Of Mass Energy ◽  
Expected Performance ◽  
Muon Tracking ◽  
Performance Gains ◽  
Important Constituent

Muons with high momentum - above 500 GeV - are an important constituent of new physics signatures in many models. Run-2 of the LHC is greatly increasing ATLAS’s sensitivity to such signatures thanks to an ever-larger dataset of such particles, enhanced further by an increase in the center-of-mass energy. The ATLAS Muon Spectrometer chamber alignment contributes significantly to the uncertainty of the reconstruction of these high-momentum objects. The proper treatment of measurements during tracking and the correct propagation of the alignment effects is extremely challenging. Recently, an innovative approach that imposes Gaussian constraints on ensembles of detector hits was implemented. It provides a significant improvement to high-momentum tracking without increasing the CPU budget. Furthermore, it allows for the verification of the expected alignment quality using high-statistics collision data. A detailed discussion of the algorithmic realization is given, the expected performance gains are presented and prospects for further applications of the approach are outlined.

scholarly journals Proton Spectra from He3+T and He3+He3 Fusion at Low Center-of-Mass Energy, with Potential Implications for Solar Fusion Cross Sections

2017 ◽  
Vol 119 (22) ◽  
Author(s):  
A. B. Zylstra ◽  
J. A. Frenje ◽  
M. Gatu Johnson ◽  
G. M. Hale ◽  
C. R. Brune ◽  
...  
Keyword(s):  
Cross Sections ◽  
Center Of Mass ◽  
Mass Energy ◽  
Center Of Mass Energy

scholarly journals Measurements of the vector boson production with the ATLAS detector

2018 ◽  
Vol 172 ◽  
pp. 03001
Author(s):  
A. Lapertosa
Keyword(s):  
Perturbative Qcd ◽  
High Precision ◽  
Cross Sections ◽  
Center Of Mass ◽  
Atlas Collaboration ◽  
Mass Energy ◽  
Ratio Measurement ◽  
Center Of Mass Energy ◽  
Proton Structure ◽  
8 Tev

Measurements of the Drell-Yan production of W and Z bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements at a center-of-mass energy of 7 TeV. The measurements are performed for W+, W- and Z bosons integrated and as a function of the boson or lepton rapidity and the Z mass. Unprecedented precision is reached and strong constraints on Parton Distribution Functions, in particular the strange density are found. Z boson cross sections are also measured at center-of-mass energies of 8 TeV and 13 TeV, and cross-section ratios to the top-quark pair production have been derived. This ratio measurement leads to a cancellation of systematic effects and allows for a high precision comparison to the theory predictions. The production of jets in association with vector bosons is a further important process to study perturbative QCD in a multi-scale environment. The ATLAS collaboration has performed new measurements of Z boson plus jets cross sections, differential in several kinematic variables, in proton-proton collision data taken at a center-of-mass energy of 13 TeV. The measurements are compared to state-of-the art theory predictions. They are sensitive to higher-order pQCD effects, probe flavour and mass schemes and can be used to constrain the proton structure. In addition, a new measurement of the splitting scales of the kt jet-clustering algorithm for final states containing a Z boson candidate at a center-of-mass energy of 8 TeV is presented.

Measurement of total and partial photon proton cross sections at 180 GeV center of mass energy

1994 ◽  
Vol 63 (3) ◽  
pp. 391-408 ◽  
Author(s):  
◽  
M. Derrick ◽  
D. Krakauer ◽  
S. Magill ◽  
B. Musgrave ◽  
...  
Keyword(s):  
Cross Sections ◽  
Center Of Mass ◽  
Mass Energy ◽  
Center Of Mass Energy
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