The high efficiency, low background, and single-photon detection with transition-edge sensors (TES) is making this type of detector attractive in widely different types of applications. In this ...paper, we present first characterizations of a TES to be used in the Any Light Particle Search (ALPS) experiment searching for new fundamental ultra-light particles. Firstly, we describe the setup and the main components of the ALPS TES detector (TES, millikelvin-cryostat and SQUID readout) and their performances. Secondly, we explain a dedicated analysis method for single-photon spectroscopy and rejection of non-photon background. Finally, we report on results from extensive background measurements. Considering an event selection, optimized for a wavelength of 1064 nm, we achieved a background suppression of
with a
% efficiency for photons passing the selection. The resulting overall efficiency was 23% with a dark count rate of
. We observed that pile-up events of thermal photons are the main background components.
A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged ...current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarization of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.
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.
Measurement of the luminosity in the ZEUS experiment at HERA II Adamczyk, L.; Andruszkow, J.; Bold, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2014, Letnik:
744
Journal Article
Recenzirano
Odprti dostop
The luminosity in the ZEUS detector was measured using photons from electron bremsstrahlung off protons. In 2001 the HERA collider was upgraded for operation at higher luminosity. At the same time ...the luminosity-measuring system of the ZEUS experiment was modified to tackle the expected higher photon rate and synchrotron radiation. The existing lead-scintillator calorimeter was equipped with radiation hard scintillator tiles and shielded against synchrotron radiation. In addition, a magnetic spectrometer was installed to measure the luminosity independently using photons converted in the beam-pipe exit window. The redundancy provided a reliable and robust luminosity determination with a systematic uncertainty of 1.7%. The experimental setup, the techniques used for luminosity determination and the estimate of the systematic uncertainty are reported.
A
bstract
The production of beauty and charm quarks in
ep
interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5
< Q
2
<
1000 GeV
2
using an integrated ...luminosity of 354 pb
−1
. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of
Q
2
, Bjorken
x
, jet trans- verse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of
x
and
Q
2
. The running beauty-quark mass,
m
b
at the scale
m
b
, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be
m
b
(
m
b
) = 4.07 ± 0.14 (fit)
− 0.07
+ 0.01
(mod.)
− 0.00
+ 0.05
(param.)
− 0.05
+ 0.08
(theo.) GeV.
A combination is presented of all inclusive deep inelastic cross sections previously published by the H1 and ZEUS collaborations at HERA for neutral and charged current $e^{\pm}p$ scattering for zero ...beam polarisation. The data were taken at proton beam energies of 920, 820, 575 and 460 GeV and an electron beam energy of 27.5 GeV. The data correspond to an integrated luminosity of about 1 fb$^{-1}$ and span six orders of magnitude in negative four-momentum-transfer squared, $Q^2$, and Bjorken $x$. The correlations of the systematic uncertainties were evaluated and taken into account for the combination. The combined cross sections were input to QCD analyses at leading order, next-to-leading order and at next-to-next-to-leading order, providing a new set of parton distribution functions, called HERAPDF2.0. In addition to the experimental uncertainties, model and parameterisation uncertainties were assessed for these parton distribution functions. Variants of HERAPDF2.0 with an alternative gluon parameterisation, HERAPDF2.0AG, and using fixed-flavour-number schemes, HERAPDF2.0FF, are presented. The analysis was extended by including HERA data on charm and jet production, resulting in the variant HERAPDF2.0Jets. The inclusion of jet-production cross sections made a simultaneous determination of these parton distributions and the strong coupling constant possible, resulting in $\alpha_s(M_Z)=0.1183 \pm 0.0009 {\rm(exp)} \pm 0.0005{\rm (model/parameterisation)} \pm 0.0012{\rm (hadronisation)} ^{+0.0037}_{-0.0030}{\rm (scale)}$. An extraction of $xF_3^{\gamma Z}$ and results on electroweak unification and scaling violations are also presented.
A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised
e
±
p
scattering at HERA during the ...period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared,
Q
2
, and in Bjorken
x
. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.
Measurements of open charm production cross sections in deep-inelastic
ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections
for charm production are obtained ...in the kinematic range of photon virtuality 2.5≤
Q
2
≤2000 GeV
2
and Bjorken scaling variable 3⋅10
−5
≤
x
≤5⋅10
−2
. The combination method accounts for the correlations of the systematic uncertainties among the different data sets. The combined charm data together with the combined inclusive deep-inelastic scattering cross sections from HERA are used as input for a detailed NLO QCD analysis to study the influence of different heavy flavour schemes on the parton distribution functions. The optimal values of the charm mass as a parameter in these different schemes are obtained. The implications on the NLO predictions for
W
±
and
Z
production cross sections at the LHC are investigated. Using the fixed flavour number scheme, the running mass of the charm quark is determined.
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