A
bstract
A comprehensive set of azimuthal single-spin and double-spin asymmetries in semi-inclusive leptoproduction of pions, charged kaons, protons, and antiprotons from transversely polarized ...protons is presented. These asymmetries include the previously published HERMES results on Collins and Sivers asymmetries, the analysis of which has been extended to include protons and antiprotons and also to an extraction in a three-dimensional kinematic binning and enlarged phase space. They are complemented by corresponding results for the remaining four single-spin and four double-spin asymmetries allowed in the one-photon-exchange approximation of the semi-inclusive deep-inelastic scattering process for target-polarization orientation perpendicular to the direction of the incoming lepton beam. Among those results, significant non-vanishing cos (
ϕ−ϕ
S
) modulations provide evidence for a sizable worm-gear (II) distribution,
g
1
T
q
x
p
T
2
. Most of the other modulations are found to be consistent with zero with the notable exception of large sin (
ϕ
S
) modulations for charged pions and
K
+
.
B-flavor tagging at Belle II Akopov, N.; Banerjee, Sw; Bauer, M. ...
The European physical journal. C, Particles and fields,
04/2022, Letnik:
82, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom (
) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor ...mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic
decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb
-
1
, collected at the
resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be
ε
eff
=
(
30.0
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a category-based algorithm and
ε
eff
=
(
28.8
±
1.2
(
stat
)
±
0.4
(
syst
)
)
%
for a deep-learning-based algorithm.
An estimate is given of the simulation with the Monte Carlo (MC) method using the signal to background ratios in invariant mass spectra of pion-kaon system for decays of
D
0
→
K
−
π
+
and
→
K
+
π
−
...originated from decays of
D
*
+
→
D
0
π
+
and
D*
−
→
π
−
at different momentum/angular bins of pions (when pion is coming to the ARICH acceptance) and kaons (kaon is in ARICH acceptance). The tabulated data for mentioned ratios will be used by Belle II collaboration to study the ARICH performance. Then the results of ARICH efficiencies and misidentification probability extracted based on tabulated ratios, will become important ingredient for future physics analysis.
The verification scheme in the package “Professor2” for setting parameters of the most used physics generator PYTHIA8.2 for simulating the processes in high energy physics is described. The goal is ...to tune the PYTHIA8.2 parameter list for the fragmentation process below
the production threshold. As an initial parameter list, we use the Belle (predecessor of the Belle II experiment) default parameter settings for fragmentation. For the MC pseudo-data, we use the Belle II software package i.e. basf2, and generator script developed by the main author of this paper. To validate the whole procedure, we use momentum distribution of charged pions and kaons to tune two free parameters of the fragmentation model in PYTHIA8 i.e. LUND fragmentation model. We demonstrate that the Professor2 package is a handful to perform multi-parameter tunes simultaneously.
The OLYMPUS experiment Milner, R.; Hasell, D.K.; Kohl, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2014, Letnik:
741
Journal Article
Recenzirano
Odprti dostop
The OLYMPUS experiment was designed to measure the ratio between the positron–proton and electron–proton elastic scattering cross-sections, with the goal of determining the contribution of two-photon ...exchange to the elastic cross-section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, μpGEp/GMp, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2.01GeV electron and positron beams incident on an internal hydrogen gas target. The experiment used a toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight detectors to measure rates for elastic scattering over the polar angular range of approximately 25°–75°. Symmetric Møller/Bhabha calorimeters at 1.29° and telescopes of GEM and MWPC detectors at 12° served as luminosity monitors. A total luminosity of approximately 4.5fb−1 was collected over two running periods in 2012. This paper provides details on the accelerator, target, detectors, and operation of the experiment.
The improved two-scale model is used to perform the fit to the semi-inclusive deep-inelastic scattering (SIDIS) data of HERMES experiment at DESY on nuclear targets. The ratio of hadron multiplicity ...on nuclear target to the deuterium one is chosen as observable, as usually. The two-parameter’s fit gives satisfactory agreement with the data in term of
χ
2
criterium. Best values of parameters are then used to calculate the nuclear multiplicity ratio for the hadrons not included in the fit procedure.
The two-scale model and its improved version were used to perform a fit to the HERMES data for the \(\nu\) (the virtual photon energy) and z (the fraction of \(\nu\) carried by hadron) dependences of ...the nuclear multiplicity ratios for \(\pi^ + \) and \(\pi^-\) mesons electro-produced on two nuclear targets (14N and 84Kr). The quantitative criterion \(\chi^2\) was used for the first time to analyze the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gave satisfactory agreement with the HERMES data. Best values of the parameters were then used to calculate the \(\nu\) and z dependences of the nuclear attenuation for \(\pi^0\), K + , K-, and \(\bar{p}\) produced on the 84Kr target, and also make predictions for \(\nu\), z, and the Q2 (the photon virtuality) dependences of the nuclear attenuation data for those identified hadrons and nuclei that will be published by HERMES.
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