A
bstract
Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity
ep
scattering at a centre-of-mass energy
s
= 318 GeV with the ZEUS detector at ...HERA. Two- and four-particle azimuthal correlations, as well as multiplicity, transverse momentum, and pseudorapidity distributions for charged-particle multiplicities
N
ch
≥ 20 are measured. The dependence of two-particle correlations on the virtuality of the exchanged photon shows a clear transition from photoproduction to neutral current deep inelastic scattering. For the multiplicities studied, neither the measurements in photoproduction processes nor those in neutral current deep inelastic scattering indicate significant collective behaviour of the kind observed in high-multiplicity hadronic collisions at RHIC and the LHC. Comparisons of PYTHIA predictions with the measurements in photoproduction strongly indicate the presence of multiparton interactions from hadronic fluctuations of the exchanged photon.
The high-precision HERA data allows searches up to TeV scales for beyond the Standard Model contributions to electron–quark scattering. Combined measurements of the inclusive deep inelastic cross ...sections in neutral and charged current ep scattering corresponding to a luminosity of around 1 fb−1 have been used in this analysis. A new approach to the beyond the Standard Model analysis of the inclusive ep data is presented; simultaneous fits of parton distribution functions together with contributions of “new physics” processes were performed. Results are presented considering a finite radius of quarks within the quark form-factor model. The resulting 95% C.L. upper limit on the effective quark radius is 0.43⋅10−16 cm.
Physics at the Large Hadron Collider (LHC) and the International
e
+
e
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Linear Collider (ILC) will be complementary in many respects, as has been demonstrated at previous generations of hadron and ...lepton colliders. This report addresses the possible interplay between the LHC and ILC in testing the Standard Model and in discovering and determining the origin of new physics. Mutual benefits for the physics programme at both machines can occur both at the level of a combined interpretation of Hadron Collider and Linear Collider data and at the level of combined analyses of the data, where results obtained at one machine can directly influence the way analyses are carried out at the other machine. Topics under study comprise the physics of weak and strong electroweak symmetry breaking, supersymmetric models, new gauge theories, models with extra dimensions, and electroweak and QCD precision physics. The status of the work that has been carried out within the LHC/ILC Study Group so far is summarized in this report. Possible topics for future studies are outlined.
Data from HERA, LEP and the Tevatron as well as from low energy experiments are used to constrain the scale of possible electron–quark contact interactions. Different models are considered, including ...the most general one, in which all new couplings can vary independently. Limits on couplings and mass scales are extracted and upper limits on possible effects to be observed in future HERA, LEP and Tevatron runnings are estimated. The total hadronic cross section at LEP and the \(e^{-}p\) scattering cross section at HERA are strongly constrained by the existing data, whereas large cross section deviations are still possible for Drell–Yan lepton pair production at the Tevatron.
The “Pi of the Sky” robotic telescope was designed to monitor a significant fraction of the sky with good time resolution and range. The main goal of the “Pi of the Sky” detector is to look for short ...timescale optical transients arising from various astrophysical phenomena, mainly for the optical counterparts of Gamma Ray Bursts (GRB). The system design, the observation methodology and the algorithms that have been developed make this detector a sophisticated instrument for looking for novae and supernovae stars and for monitoring blasars and AGNs activity. The final detector will consist of two sets of 12 cameras, one camera covering a field of view of 20◦ ×20◦. For data taken with the prototype detector at the Las Campanas Observatory, Chile, photometry uncertainty of 0.018–0.024 magnitudo for stars 7–10m was obtained. With a new calibration algorithm taking into account the spectral type of reference stars, the stability of the photometry algorithm can be significantly improved. Preliminary results from the BGInd variable are presented, showing that uncertainty of the order of 0.013 can be obtained.
A Large Hadron Electron Collider at CERN Fernandez, J L Abelleira
Journal of physics. G, Nuclear and particle physics,
07/2012, Letnik:
39, Številka:
7
Journal Article
Recenzirano
Odprti dostop
The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, to ...possibly 140 GeV, energy collides with the intense hadron beams of the LHC. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. A design study is also presented of a detector suitable to perform high precision DIS measurements in a wide range of acceptance using state-of-the art detector technology, which is modular and of limited size enabling its fast installation. The LHeC can be built within a decade and thus be operated while the LHC runs in its high-luminosity phase. It so represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.
The azimuthal correlation angle, \(\Delta\phi\), between the scattered lepton and the leading jet in deep inelastic \(e^{\pm}p\) scattering at HERA has been studied using data collected with the ZEUS ...detector at a centre-of-mass energy of \(\sqrt{s} = 318 \;\mathrm{GeV}\), corresponding to an integrated luminosity of \(326 \;\mathrm{pb}^{-1}\). A measurement of jet cross sections in the laboratory frame was made in a fiducial region corresponding to photon virtuality \(10 \;\mathrm{GeV}^2 < Q^2 < 350 \;\mathrm{GeV}^2\), inelasticity \(0.04 < y < 0.7\), outgoing lepton energy \(E_e > 10 \;\mathrm{GeV}\), lepton polar angle \(140^\circ < \theta_e < 180^\circ\), jet transverse momentum \(2.5 \;\mathrm{GeV} < p_\mathrm{T,jet} < 30 \;\mathrm{GeV}\), and jet pseudorapidity \(-1.5 < \eta_\mathrm{jet} < 1.8\). Jets were reconstructed using the \(k_\mathrm{T}\) algorithm with the radius parameter \(R = 1\). The leading jet in an event is defined as the jet that carries the highest \(p_\mathrm{T,jet}\). Differential cross sections, \(d\sigma/d\Delta\phi\), were measured as a function of the azimuthal correlation angle in various ranges of leading-jet transverse momentum, photon virtuality and jet multiplicity. Perturbative calculations at \(\mathcal{O}(\alpha_{s}^2)\) accuracy successfully describe the data within the fiducial region, although a lower level of agreement is observed near \(\Delta\phi \rightarrow \pi\) for events with high jet multiplicity, due to limitations of the perturbative approach in describing soft phenomena in QCD. The data are equally well described by Monte Carlo predictions that supplement leading-order matrix elements with parton showering.
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