Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of $Q^2$.
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The transition between photoproduction and deep-inelastic scattering is investigated in jet production at the HERA ep collider, using data collected by the H1 experiment. Measurements of the differential inclusive jet cross-sections dsigep/dEt* and dsigmep/deta*, where Et* and eta* are the transverse energy and the pseudorapidity of the jets in the virtual photon-proton centre of mass frame, are presented for 0 < Q2 < 49 GeV2 and 0.3 < y < 0.6. The interpretation of the results in terms of the structure of the virtual photon is discussed. The data are best described by QCD calculations which include a partonic structure of the virtual photon that evolves with Q2.
The ET differential jet cross section in the virtual-photon CM frame.
The ET differential jet cross section in the virtual-photon CM frame.
The ET differential jet cross section in the virtual-photon CM frame.
This paper presents the first analysis of diffractive photon dissociation events in deep inelastic positron-proton scattering at HERA in which the proton in the final state is detected and its momentum measured. The events are selected by requiring a scattered proton in the ZEUS leading proton spectrometer (LPS) with $\xl>0.97$, where $\xl$ is the fraction of the incoming proton beam momentum carried by the scattered proton. The use of the LPS significantly reduces the contamination from events with diffractive dissociation of the proton into low mass states and allows a direct measurement of $t$, the square of the four-momentum exchanged at the proton vertex. The dependence of the cross section on $t$ is measured in the interval $0.073<|t|<0.4$~$\gevtwo$ and is found to be described by an exponential shape with the slope parameter $b=\tslopeerr$. The diffractive structure function $\ftwodfour$ is presented as a function of $\xpom \simeq 1-\xl$ and $\beta$, the momentum fraction of the struck quark with respect to $\xpom$, and averaged over the $t$ interval $0.073<|t|<\ftwodfourtmax$~$\gevtwo$ and the photon virtuality range $5<Q^2<20~\gevtwo$. In the kinematic range $4 \times 10^{-4} < \xpom < 0.03$ and $0.015<\beta<0.5$, the $\xpom$ dependence of $\ftwodfour$ is fitted with a form $\xpoma$, yielding $a= \ftwodfouraerr$. Upon integration over $t$, the structure function $\ftwod$ is determined in a kinematic range extending to higher $\xpom$ and lower $\beta$ compared to our previous analysis; the results are discussed within the framework of Regge theory.
The measured distribution of T, the squared momentum transfer to the virtual pluton.
Slope of the T distribution.
The structure function F2(NAME=D4).
The double-differential inclusive di-jet cross section in photoproduction processes is measured with the H1 detector at HERA. The cross section is determined as a function of the average transverse jet energy E_T^jets for ranges of the fractional energy x_gamma^jets of the parton from the photon side. An effective leading order parton distribution in the photon is determined at large parton fractional energies for scales between 80<p_T^2<1250 GeV^2. The measurement is compatible with the logarithmic scale dependence that is predicted by perturbative QCD.
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Polarized and unpolarized proton-proton elastic scattering is investigated with the EDDA-experiment at the Cooler Synchrotron COSY at Jülich to significantly improve the world data base in the beam energy range 500–2500 MeV. Measurements during beam acceleration with thin internal targets and a large acceptance detector provide excitation functions over a broad angular and energy range with unprecedented internal consistency. Data taking with an unpolarized CH2 fiber target and an unpolarized beam have been completed and the derived differential cross sections are presented and compared to a recent phase shift analysis. With a polarized atomic beam target newly installed in COSY and a polarized COSY beam—currently under development—the measurements will be extended to analyzing powers and spin correlation parameters.
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Data from Rohdjess dissertation.
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A measurement of the strong coupling constant α S is presented using hadronic events produced in e + e − annihilations at s =58.0 GeV from the AMY detector at TRISTAN. The measurement is based on comparisons of the distributions of thrust, heavy jet mass, total jet broadening, wide jet broadening, and energy-energy correlations with QCD calculations resummed up to next-to-leading-logarithms matched with the O ( α S 2 ) perturbative calculation. Combining the results of the individual evaluations, we find α S (58 GeV )=0.132±0.006 .
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The muon capture rate in the reaction mu- 3He -> nu + 3H has been measured at PSI using a modular high pressure ionization chamber. The rate corresponding to statistical hyperfine population of the mu-3He atom is (1496.0 +- 4.0) s^-1. This result confirms the PCAC prediction for the pseudoscalar form factors of the 3He-3H system and the nucleon.
Here CONST is defined as follows: CONST = lambda0/K/(1-e), where lambda0 = 0.45516E6 1/sec is the decay rate of MU, e=7.18% is the total correction factor and K is the prescaling factor of the muon trigger (from 500 till 2000). First reaction corresponds to detected tritons, while the second one describes stopped muons not followed by muon capture. The error is the combination of statistical and systematic errors.
We present a new measurement of the virtual photon proton asymmetry A 1 p from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0.0008 < x < 0.7 and 0.2 < Q 2 < 100 GeV 2 . With this, the statistical uncertainty of our measurement has improved by a factor of 2 compared to our previous measurements. The spin-dependent structure function g 1 p is determined for the data with Q 2 > 1 GeV 2 . A perturbative QCD evolution in next-to-leading order is used to determine g 1 p ( x ) at a constant Q 2 . At Q 2 = 10 GeV 2 we find, in the measured range, ∫ 0.003 0.7 g 1 P (x) d x=0.139±0.006 ( stat ) ±0.008 ( syst ) ±0.006( evol ) . The value of the first moment Г 1 P = ∫ 0 1 g 1 p (x) d x of g 1 p depends on the approach used to describe the behaviour of g 1 p at low x . We find that the Ellis-Jaffe sum rule is violated. With our published result for Γ 1 d we confirm the Bjorken sum rule with an accuracy of ≈ 15% at the one standard deviation level.
The virtual photon proton asymmetries. Only statistical errors are given.
The virtual photon proton asymmetries A1 and the spin dependent structure function G1.
The spindependent tructure function G1 evolved to Q2 = 10 GEV**2.. The second DSYS for this indicates the uncertainty in the QCD evolution.
The data collected by DELPHI in 1996 have been used to measure the average charged particle multiplicities and dispersions in q q ̄ events at centre-of-mass energies of s =161 GeV and s =172 GeV, and the average charge multiplicity in WW events at s =172 GeV. The multiplicities in q q ̄ events are consistent with the evolution predicted by QCD. The dispersions in the multiplicity distributions are consistent with Koba-Nielsen-Olesen (KNO) scaling. The average multiplicity of charged particles in hadronic W decays has been measured for the first time; its value, 19.23±0.74(stat+syst), is consistent with that expected for an e + e − interaction at a centre-of-mass energy equal to the W mass. The charged particle multiplicity in W decays shows no evidence of effects of colour reconnection between partons from different W's at the present level of statistics.
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Results are presented on p + ω,ø and J/ψ production in p-W and 32S-W interactions at 200GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio Bσø/ (Bσρ + Bσω), where B is the relevant resonance µµ branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S-W interactions. This results from an increase in the number of produced ø’s per charged particle. The ratio is measured in different intervals of pt and rapidity. It is not clearly dependent on pt, but is larger at higher rapidities. J/Ψ production, likewise normalized to charged multiplicity, is significantly lower in S-W compared to p-W interactions.
Multiplicity dependence of the ratios for proton beam.
Multiplicity dependence of the ratios for sulphur beam.
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