3,824 research outputs found

    Energy Dependence of the Pomeron Spin-Flip

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    There is no theoretical reason to think that the spin-flip component of the Pomeron is zero. One can measure the spin-flip part using Coulomb-nuclear interference (CNI). Perturbative QCD calculations show that the spin-flip component is sensitive to the smallest quark separation in the proton, while the non-flip part probes the largest separation. According to HERA results on the proton structure function at very low x the energy dependence of the cross-section correlates with the size of the color dipole. Analysing the data from HERA we predict that the ratio of the spin-flip to non-flip amplitude grows with energy as r(s)∝(1/x)0.1−0.2r(s)\propto (1/x)^{0.1-0.2}, violating Regge factorisation of the Pomeron.Comment: A few comments and references are added. Based on invited talks at the International Workshop on Diffraction Physics, Rio de Janeiro, February 16-20, 1998, and at DIS'98, Brussels, April 4-8, 199

    Form of analyzing power and the determination of the basic parameters of hadron scattering amplitude

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    The determination of magnitudes of basic parameters of the high energy elastic scattering amplitude are examined at small momentum transfers with taking account of the Coulomb-hadron interference effects.Comment: 6 pages, LaTeX, 4 figures (files.ps), Talk at the International Workshop "Spin and Symmetry" (Prague, Chech., 13-19 July 2000

    ILC Beam Energy Measurement by means of Laser Compton Backscattering

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    A novel, non-invasive method of measuring the beam energy at the International Linear Collider is proposed. Laser light collides head-on with beam particles and either the energy of the Compton scattered electrons near the kinematic end-point is measured or the positions of the Compton backscattered γ\gamma-rays, the edge electrons and the unscattered beam particles are recorded. A compact layout for the Compton spectrometer is suggested. It consists of a bending magnet and position sensitive detectors operating in a large radiation environment. Several options for high spatial resolution detectors are discussed. Simulation studies support the use of an infrared or green laser and quartz fiber detectors to monitor the backscattered photons and edge electrons. Employing a cavity monitor, the beam particle position downstream of the magnet can be recorded with submicrometer precision. Such a scheme provides a feasible and promising method to access the incident beam energy with precisions of 10−410^{-4} or better on a bunch-to-bunch basis while the electron and positron beams are in collision.Comment: 47 pages, 26 figures, version as accepted by Nucl. Instr. Meth. A after improvement

    Dual-Readout Calorimetry with Lead Tungstate Crystals

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    Results are presented of beam tests in which a small electromagnetic calorimeter consisting of lead tungstate crystals was exposed to 50 GeV electrons and pions. This calorimeter was backed up by the DREAM Dual-Readout calorimeter, which measures the scintillation and \v{C}erenkov light produced in the shower development, using two different media. The signals from the crystal calorimeter were analyzed in great detail in an attempt to determine the contributions from these two types of light to the signals, event by event. This information makes it possible to eliminate the dominating source of fluctuations and thus achieve an important improvement in hadronic calorimeter performance.Comment: Preprint submitted to Nucl. Instrum. Meth. on July 23, 200

    Impact of saturation on spin effects in proton-proton scattering

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    For pomerons described by a sum of two simple-pole terms, a soft and a hard pomeron, the unitarity bounds from saturation in impact-parameter space are examined. We consider the effect of these bounds on observables linked with polarisation, such as the analyzing power in elastic proton-proton scattering, for LHC energies. We obtain the s and t dependence of the Coulomb-nuclear interference at small momentum transfer, and show that the effect of the hard pomeron may be observed at the LHC.Comment: 8 pages, 2 figures, presented by O.V.S. at the Advanced Studies Institute "Symetries and Spin" (SPIN-Praha-2004), Prague, July 5 - July 10, 200

    Study of the electron trigger efficiency of the CMS Experiment using test beam data

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    A study of the electron identification and selection efficiency of the L1 Trigger algorithm has been performed using the combined ECAL/HCAL test beam data. A detailed discussion of the electron isolation and its impact on the selection efficiency is presented. The L1 electron algorithm is studied for different beam energies and the results indicate that efficiencies of 98% or more can be achieved for electrons with energies between 15 and 100 GeV. The fraction of charged hadrons with energies from 3 up to 100 GeV rejected by the L1 electron trigger algorithm is estimated to be larger than 93%.Comment: 22 pages, 14 figure

    Search for a Standard Model Higgs Boson in CMS via Vector Boson Fusion in the H->WW->l\nu l\nu Channel

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    We present the potential for discovering the Standard Model Higgs boson produced by the vector-boson fusion mechanism. We considered the decay of Higgs bosons into the W+W- final state, with both W-bosons subsequently decaying leptonically. The main background is ttbar with one or more jets produced. This study is based on a full simulation of the CMS detector, and up-to-date reconstruction codes. The result is that a signal of 5 sigma significance can be obtained with an integrated luminosity of 12-72 1/fb for Higgs boson masses between 130-200 GeV. In addition, the major background can be measured directly to 7% from the data with an integrated luminosity of 30 1/fb. In this study, we also suggested a method to obtain information in Higgs mass using the transverse mass distributions.Comment: 26 pages, 22 figure

    The effects of the small t properties of hadronic scattering amplitude on the determination its real part

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    Taking into account the different forms of the Coulomb-hadron interference phase and the possible spin-flip contribution the new analysis of the experimental data of the proton-antiproton elastic scattering at 3.8<pL<6.0 3.8 < p_L <6.0 \ GeV/c and small momentum transfer is carried out. It is shown that the size of the spin-flip amplitude can be determined from the form of the differential cross sections at small tt, and the deviation of ρ(s,t)\rho(s,t) obtained from the examined experimental data of the ppˉp\bar{p} scattering from the analysis \cite{Kroll}, based on the dispersion relations, is conserved in all xamined assumptions. The analysis of the proton-proton elastic scattering at 9<pL<70 9 < p_L < 70 \ GeV/c also shows the impact of the examined effects on the form of the differential cross sections.Comment: 13 pages, 3 figure