The Cosmic Ray Tracking (CRT) detector system Bernlöhr, K.; Gamp, S.; Hermann, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/1996, Letnik:
369, Številka:
1
Journal Article
Recenzirano
The Cosmic Ray Tracking (CRT) project represents a study on the use of tracking detectors of the time projection chamber type to detect secondary cosmic ray particles in extensive air showers. In ...reconstructing the arrival direction of the primary cosmic ray particles, the CRT detectors take advantage of the angular correlation of secondary particles with the cosmic rays leading to these air showers.
In this paper, the detector hardware including the custom-designed electronics system is described in detail. A CRT detector module provides an active area of 2.5 m
2 and allows to measure track directions with a precision of 0.4°. It consists of two circular drift chambers of 1.8 m diameter with six sense wires each, and a 10cm thick iron plate between the two chambers. Each detector has a local electronics box with a readout, trigger, and monitoring system.
The detectors can distinguish penetrating muons from other types of charged secondaries. A large detector array could be used to search for
γ-ray point sources at energies above several TeV and for studies of the cosmic-ray composition. Ten detectors are in operation at the site of the HEGRA air shower array.
The DIS diffractive cross section, , has been measured in the mass range GeV for c.m. energies GeV and photon virtualities to 140 GeV. For fixed and , the diffractive cross section rises rapidly with ..., with corresponding to a t-averaged pomeron trajectory of which is larger than observed in hadron-hadron scattering. The W dependence of the diffractive cross section is found to be the same as that of the total cross section for scattering of virtual photons on protons. The data are consistent with the assumption that the diffractive structure function factorizes according to . They are also consistent with QCD based models which incorporate factorization breaking. The rise of with decreasing and the weak dependence of on suggest a substantial contribution from partonic interactions.
The photoproduction reaction
γp→
μ
+μ
−p
has been studied in
ep interactions using the ZEUS detector at HERA. The data sample corresponds to an integrated luminosity of
43.2
pb
−1
. The
ϒ meson has ...been observed in photoproduction for the first time. The sum of the products of the elastic
ϒ(1
S),
ϒ(2
S),
ϒ(3
S) photoproduction cross sections with their respective branching ratios is determined to be 13.3±6.0(
stat.)
+2.7
−2.3(
syst.) pb at a mean photon-proton centre of mass energy of 120 GeV. The cross section is above the prediction of a perturbative QCD model.
Elastic and proton–dissociative photoproduction of \(\rho^0\), \(\phi\) and \(J/\psi\) vector mesons (\(\gamma p\rightarrow Vp\), \(\gamma p\rightarrow VN\), respectively) have been measured in ...\(e^+p\) interactions at HERA up to \(-t=3\) GeV\(^2\), where t is the four-momentum transfer squared at the photon–vector–meson vertex. The analysis is based on a data sample in which photoproduction reactions were tagged by detection of the scattered positron in a special-purpose calorimeter. This limits the photon virtuality, \(Q^2\), to values less than 0.01 GeV\(^2\), and selects a \(\gamma p\) average center-of-mass energy of \(\langle W\rangle\) = 94 GeV. Results for the differential cross sections, \(\mbox{d}\sigma/\mbox{d}t\), for \(\rho^0\), \(\phi\) and \(J/\psi\) mesons are presented and compared to the results of recent QCD calculations. Results are also presented for the t-dependence of the pion-pair invariant-mass distribution in the \(\rho^0\) mass region and of the spin-density matrix elements determined from the decay-angle distributions. The Pomeron trajectory has been derived from measurements of the W dependence of the elastic differential cross sections \(\mbox{d}\sigma/\mbox{d}t\) for both \(\rho^0\) and \(\phi\) mesons.
This paper presents measurements of D{sup *{+-}} production in deep inelastic scattering from collisions between 27.5 GeV positrons and 820 GeV protons. The data have been taken with the ZEUS ...detector at HERA. The decay channel D{sup *+} {yields} (D{sup 0} {yields} K{sup -}{pi}{sup +}){pi}{sup +} (+c.c) has been used in the study. The e{sup +}p cross section for inclusive D{sup *{+-}} production with 5 <Q{sup 2} < 100 GeV{sup 2}> and y < 0.7 is 5.3 {+-} 1.0 {+-} 0.8 nb in the kinematic region 1.3 < p{sub T}(D{sup *{+-}}) < 9.0 GeV and |{eta}(D{sup *{+-}})| < 1.5. Differential cross sections as functions of p{sub T}(D{sup *{+-}}), {eta}(D{sup *{+-}}), W and Q{sup 2} are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in p{sub T}(D{sup *{+-}}) and {eta}(D{sup *{+-}}), the charm contribution F{sub 2}{sup c}{bar c}(x, Q{sup 2}) to the proton structure function is determined for Bjorken x between 2 x 10{sup -4} and 5 x 10{sup -3}.
The exclusive electroproduction of
ω mesons,
ep→
eωp, has been studied in the kinematic range 3<
Q
2<20 GeV
2, 40<
W<120 GeV and |
t|<0.6 GeV
2 with the ZEUS detector at HERA using an integrated ...luminosity of 37.7 pb
−1. The
ω mesons were identified via the decay
ω→
π
+
π
−
π
0. The exclusive cross section in the above kinematic region is
σ
ep→
eωp
=0.108±0.014(stat.)±0.026(syst.) nb. The reaction
ep→
eφp,
φ→
π
+
π
−
π
0, has also been measured. The cross sections, as well as the ratios
σ
γ
∗p→ωp
/σ
γ
∗p→ρ
0p
and
σ
γ
∗p→ωp
/σ
γ
∗p→φp
, are presented as a function of
W and
Q
2. Thus, for the first time, the properties of
ω electroproduction can be compared to those of
ρ
0,
φ and
J/
ψ electroproduction at high
W.
First inclusive measurements of isolated prompt photons in photoproduction at the HERA
ep collider have been made with the ZEUS detector, using an integrated luminosity of 38.4 pb
−1. Cross sections ...are given as a function of the pseudorapidity and the transverse energy (
η
γ
,
E
T
γ
) of the photon, for
E
T
γ
>5
GeV in the
γp centre-of-mass energy range 134–285 GeV. Comparisons are made with predictions from Monte Carlo models having leading-logarithm parton showers, and with next-to-leading-order QCD calculations, using currently available parameterisations of the photon structure. For forward
η
γ
(proton direction) good agreement is found, but in the rear direction all predictions fall below the data.
The distribution of the azimuthal angle for the charged hadrons has been studied in the hadronic centre-of-mass system for neutral current deep inelastic positron–proton scattering with the ZEUS ...detector at HERA. Measurements of the dependence of the moments of this distribution on the transverse momenta of the charged hadrons are presented. Asymmetries that can be unambiguously attributed to perturbative QCD processes have been observed for the first time.
The production of φ mesons in the reaction
e
+
p →
e
+
φp (
gf →
K
+
K
−) at a median
Q
2 of 10
−4 GeV
2 h been studied with the ZEUS detector at HERA. The differential φ photoproduction cross ...section
dσ
dt
has an exponential shape and has been determined in the kinematic range 0.1 < |
t| < 0.5 GeV
2 and 60 <
W < 80 GeV. An integrated cross sect
σ
γp→
φp
= 0.96±0.19
−0.18
+0.21
μb has been obtained by extrapolating to
t = 0. When compared to lower energy data the results show a weak energy dependence of both
σ
γp→
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.
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