-
ZEUS Collaboration,
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J. R. Okrasinski,
J. Repond,
R. Stanek,
R. L. Talaga, [......],
S. Silverstein,
W. H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M. L. Cardy,
W. R. Frisken,
M. Khakzad,
W. N. Murray,
W. B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: Deep inelastic charged-current reactions have been studied ine
+
p ande
−
p collisions at a center of mass energy of about 300GeV in the kinematic regionQ
2>200GeV2 andx>0.006 using the ZEUS detector at HERA. The integrated cross sections forQ
2>200GeV2 are found to be se+ p ® [`(n)] X = 30.3 - 4.2 - 2.6 + 5.5 + 1.6 pb\sigma _{e^ + p \to \bar \nu X} = 30.3_{ - 4.2 - 2.6}^{ + 5.5 + 1.6} pb and se- p ® nX = 54.7 - 9.8 - 3.4 + 15.9 + 2.8 pb\sigma _{e^ - p \to \nu X} = 54.7_{ - 9.8 - 3.4}^{ + 15.9 + 2.8} pb. Differential cross sections have been measured as functions of the variablesx, y andQ
2. From the measured differential cross sectionsdσ/dQ
2, theW boson mass is determined to be MW = 79 - 7 - 4 + 8 + 4 GeVM_W = 79_{ - 7 - 4}^{ + 8 + 4} GeV. Measured jet rates and transverse energy profiles agree with model predictions. A search for charged-current interactions
with a large rapidity gap yielded one candidate event, corresponding to a cross section of $\sigma _{e^ + p \to \bar \nu X} (Q^2 > 200 GeV^2 ; \eta _{\max }< 2.5) = 0.8_{ - 0.7}^{ + 1.8} \pm 0.1 pb$\sigma _{e^ + p \to \bar \nu X} (Q^2 > 200 GeV^2 ; \eta _{\max }< 2.5) = 0.8_{ - 0.7}^{ + 1.8} \pm 0.1 pb
Zeitschrift für Physik C 04/1996; 72(1):47-64.
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ZEUS Collaboration,
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J. R. Okrasinski,
J. Repond,
R. Stanek,
R. L. Talaga, [......],
S. Silverstein,
W. H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M. L. Cardy,
W. R. Frisken,
M. Khakzad,
W. N. Murray,
W. B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: We present measurements of the structure functionF
2 ine
+
p scattering at HERA in the range 3.5 GeV2<Q
2<5000 GeV2. A new reconstruction method has allowed a significant improvement in the resolution of the kinematic variables and an extension
of the kinematic region covered by the experiment. AtQ
2<35 GeV2 the range inx now spans 6.3·10−5<x<0.08 providing overlap with measurements from fixed target experiments. At values ofQ
2 above 1000 GeV2 thex range extends to 0.5. Systematic errors below 5% have been achieved for most of the kinematic region. The structure function
rises asx decreases; the rise becomes more pronounced asQ
2 increases. The behaviour of the structure function data is well described by next-to-leading order perturbative QCD as implemented
in the DGLAP evolution equations.
Zeitschrift für Physik C 04/1996; 72(3):399-424.
-
J. Breitweg,
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave,
J. Repond,
R. Stanek,
R. L. Talaga,
R. Yoshida, [......],
R. J. Loveless,
S. Mattingly,
D. D. Reeder,
W. H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
W. R. Frisken,
M. Khakzad,
W. B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: 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
L
> 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 ont is measured in the interval 0.073 t| < 0.4="">2 and is found to be described by an exponential shape with the slope parameterb = 7.2 1.1(stat.)
–0.9
+0.7
(syst.) GeV–2. The diffractive structure function FD (4) is presented as 0.9 a function of
H
1 –
L
and , the momentum fraction of the struck quark with respect to
H
, and averaged over thet interval 0.073 < 0.4="">2 and the photon virtuality range 5 Q
2 < 20="">2. In the kinematic range 4 104
p
< 0.03="" and="" 0.015=""> < 0.5,="" the="">
p
dependence ofF
D(4) is fitted with a form (1/
p
) , yieldinga – 1.00 0.09 (stat.)
–0.05
+0.11
(syst.). Upon integration overL, the structure functionF
2
D(3) is determined in a kinematic range extending to higher
p
and lower compared to our previous analysis; the results are discussed within the framework of Regge theory.
Zeitschrift für Physik C 01/1979; 1(1):81-96.
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M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang,
G. Bari, [......],
M. Wodarczyk,
T. Tsurugai,
S. Bhadra,
M.L. Cardy,
C.-P. Fagerstroem,
W.R. Frisken,
K.M. Furutani,
M. Khakzad,
W.N. Murray,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: Photoproduction events which have two or more jets have been studied in the Wγp range 135 GeV < Wγp < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Δη) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of Δη. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of Δη ∼ 3, then reaches a cconstant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.
Physics Letters B.
-
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang,
R. Ayad, [......],
A. Vaiciulis,
M. Wodarczyk,
T. Tsurugai,
S. Bhadra,
M.L. Cardy,
C.-P. Fagerstroem,
W.R. Frisken,
K.M. Furutani,
M. Khakzad,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: Jet production in deep inelastic scattering for 120 < 2 < 3600 GeV2 has been studied using data from an integrated luminosity of 3.2 pb−1 collected with the ZEUS detector at HERA. Jets are identified with the JADE algorithm. A cut on the angular distribution of parton emission in the centre-of-mass system minimises the experimental and theoretical uncertainties in the determination of the jet rates. The jet rates, when compared to (αs2) perturbative QCD calculations, allow a precise determination of αs() in three 2-intervals. The values are consistent with a running of ifαs(), as expected from QCD. Extrapolating to = MZ0αs(MZ0) = 0.117 ± 0.005 (stat) −0.005+0.004 (systexp) ± 0.007 (systtheory).
Physics Letters B.
-
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J.R. Okrasinski,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang, [......],
S. Silverstein,
W.H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M.L. Cardy,
W.R. Frisken,
M. Khakzad,
W.N. Murray,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: Jet photoproduction, where the two highest transverse energy (ETjet) jets have ETjet above 6 GeV and a jet-jet invariant mass above 23 GeV, has been studied with the ZEUS detector at the HERA ep collider. Resolved and direct photoproduction samples have been separated. The cross section as a function of the angle between the jet-jet axis and the beam direction in the dijet rest frame has been measured for the two samples. The measured angular distributions differ markedly from each other. They agree with the predictions of QCD calculations, where the different angular distributions reflect the different spins of the quark and gluon exchanged in the hard subprocess.
Physics Letters B.
-
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J.R. Okrasinski,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang, [......],
S. Silverstein,
W.H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M.L. Cardy,
W.R. Frisken,
M. Khakzad,
W.N. Murray,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: The production of φ mesons in the reaction e+p → e+φp (φ → K+K−), for and virtual photon-proton centre of mass energies (W) in the range 42–134 GeV, has been studied with the ZEUS detector at HERA. When compared to lower energy data at similar 2, the results show that the γ∗p → φp cross section rises strongly with W. This behaviour is similar to that previously found for the γ∗p → ϱ0p cross section. This strong dependence cannot be explained by production through soft pomeron exchange. It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of , which has previously been determined by ZEUS to be 0.065 ± 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 ± 0.05 (stat.) ± 0.03 (syst.) at a mean 2 of 12.3 GeV2 and mean W of ≈ 100 GeV and is thus approaching at large 2 the value of predicted from the quark charges of the vector mesons and a flavour independent production mechanism.
Physics Letters B.
-
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J.R. Okrasinski,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang, [......],
W.H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M.L. Cardy,
W.R. Frisken,
K.M. Furutani,
M. Khakzad,
W.N. Murray,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: In deep inelastic neutral current scattering of positrons and protons at the center of mass energy of 300 GeV, we observe, with the ZEUS detector, events with a high energy neutron produced at very small scattering angles with respect to the proton direction. The events constitute a fixed fraction of the deep inelastic, neutral current event sample independent of Bjorken x and Q2 in the range 3 · 10−4 < xBJ < 6 · 10−3 and 10 < Q2 < 100 GeV2.
Physics Letters B.
-
M. Derrick,
D. Krakauer,
S. Magill,
D. Mikunas,
B. Musgrave, J.R. Okrasinski,
J. Repond,
R. Stanek,
R.L. Talaga,
H. Zhang, [......],
W.H. Smith,
A. Vaiciulis,
M. Wodarczyk,
S. Bhadra,
M.L. Cardy,
C.-P. Fagerstroem,
W.R. Frisken,
M. Khakzad,
W.N. Murray,
W.B. Schmidke
[show abstract]
[hide abstract]
ABSTRACT: The production of φ mesons in the reaction e+p → e+φp (gf → K+K−) at a median Q2 of 10−4 GeV2 h been studied with the ZEUS detector at HERA. The differential φ photoproduction cross section has an exponential shape and has been determined in the kinematic range 0.1 < |t| < 0.5 GeV2 and 60 < W < 80 GeV. An integrated cross sect σγp→φp = 0.96±0.19−0.18+0.21μb has been obtained by extrapolating to t = 0. When compared to lower energy data the results show a weak energy dependence of both σγp→φp and the slope of the t distribution. The φ decay angular distributions are consistent with s-channel helicity conservation. From lower energies to HERA energies, the features of φ photoproduction are compatible with those of a soft diffractive process.
Physics Letters B.
-
J Breitweg,
S. Chekanov,
M Derrick,
D Krakauer,
S Magill,
B Musgrave,
A Pellegrino,
J Repond,
R Stanek,
R Yoshida, [......],
S Dhawan,
V. W. Hughes,
S Bhadra,
C Catterall,
J.E. Cole,
W R Frisken,
R Hall-Wilton,
M Khakzad,
S Menary,
ZEUS Collaboration
[show abstract]
[hide abstract]
ABSTRACT: A study of the ν̅ -jet mass spectrum in e+p⃗ν̅ X events at a center-of-mass energy 300 GeV has been performed with the ZEUS detector at the HERA collider at DESY using an integrated luminosity of 47.7 pb-1. The mass spectrum is in good agreement with that expected from standard model processes over the ν̅ -jet mass range studied. No significant excess attributable to the decay of a narrow resonance is observed. By using both e+p⃗e+X and e+p⃗ν̅ X data, mass-dependent limits are set on the s-channel production of scalar and vector resonant states. Couplings to first-generation quarks are considered and limits are presented as a function of the e+q and ν̅ q branching ratios. These limits are used to constrain the production of leptoquarks and R-parity violating squarks.
-
Malcolm Derrick,
D A Krakauer,
S Magill,
D Mikunas,
B Musgrave, J.R. Okrasinski,
J Repond,
R Stanek,
R L Talaga,
H Zhang, [......],
A W Vaiciulis,
M Wodarczyk,
S Bhadra,
M L Cardy,
C P Fagerstroem,
W R Frisken,
K M Furutani,
M Khakzad,
W N Murray,
W.B. Schmidke
-
A. Bamberger,
H. Boterenbrood,
J. Bulmahn,
R. Carlin,
H. Cunitz,
J. Dawson,
M. de Kamps,
W. Hain,
D. Hanna,
J. Hauschildt, [......],
G. Pitacco,
J. Repond,
S. Ritz,
M. Rohde,
J. Schlereth,
W. Schott,
R. Talaga,
H. Tiecke,
W. Verkerke,
J.J. Whitmore
[show abstract]
[hide abstract]
ABSTRACT: The design, construction, installation, and performance of the small angle rear tracking detector of the ZEUS experiment are described. The results on electron position measurement, electron energy correction, and background reduction at the first-level trigger are presented. The impact on the measurement of the proton structure function is discussed.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
