1,993 research outputs found
Measurement of Collins asymmetries in inclusive production of pion pairs in e^+e^- collisions at BABAR
We present a preliminary measurement of the Collins asymmetries in the
inclusive process e^+e^- --> qqbar --> pi pi X at center-of-mass energy near
10.6 GeV. We use a data sample of 468 fb^(-1) collected by the BABAR
experiment, and we consider pairs of charged pions produced in opposite jets in
hadronic events. We confirm a non-zero Collins effect as observed by previous
experiments, and we study the Collins asymmetry as a function of pion
fractional energies and transverse momenta, and as a function of the polar
angle of the analysis axis.Comment: 7 pages, 7 postscript figues, contributed to the Proceedings of the
36th International Conference on High Energy Physic
Study of Collins Asymmetries at BaBar
Transversity distribution describes the quark transverse polarization inside
a transversely polarized nucleon. It is the less known leading-twist piece of
the QCD description of the partonic structure of the nucleon. Transversity can
be extracted from semi-inclusive deep inelastic scattering (SIDIS) where,
however, it couples to a new, unknown fragmentation function, called Collins
function. We present the preliminary results of the measurement of the
azimuthal asymmetries in the process e^+e^- -> qqbar -> pi pi X, where the two
pions are produced in opposite hemispheres. These preliminary results are based
on a data sample of about 45 fb^{-1}, collected by the BABAR experiment at a
center-of-mass energy of 10.54 GeV, and are compared with the Belle
measurements.Comment: 6 pages, 4 postscript figues, contributed to the Proceedings of
Transversity 201
Measurement of Collins asymmetries in the inclusive production of hadron pairs
Transversity distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where it couples to a new, unknown fragmentation function, called Collins function. The aim of the analysis is a measurement of the azimuthal xasymmetries in e+e− → ππX (inclusive hadron production), based on the full BaBar data sample in order to extract the Collins fragmentation function from the measured asymmetries
Measurement of Collins asymmetries in the inclusive production of hadron pairs
Transversity distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where it couples to a new, unknown fragmentation function, called Collins function. The aim of the analysis is a measurement of the azimuthal xasymmetries in e+e− → ππX (inclusive hadron production), based on the full BaBar data sample in order to extract the Collins fragmentation function from the measured asymmetries
Measurement of Collins asymmetries at BaBar
Inclusive hadron production cross sections and angular distributions in e+e− collisions shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of the so-called Collins azimuthal
asymmetries in inclusive production of hadron pairs in e+e− → h1h2X annihilation process, where the two hadrons (either kaons or pions) are produced in opposite hemispheres. In particular, this is the first measurement in e+e−
annihilation experiment of the KK and KÏ€ azimuthal asymmetries, which allow to better understand the fragmentation processes and the role of the strage quark, and can be used as a tool to explore the spin content of the nucleon
Recent results for the BESIII experiment
Since 2009, the BESIII experiment collected data in the center-ofenergy range from 2 to 4.6 GeV, thus making it a unique environment to cover a broad range of physics topics. In this paper a selection of the recent BESIII results on the still mysterious XY Z states, hadron spectroscopy, as well as a very brief review on the charm and Λc physics are reported
Habitat Preferences of Italian Freshwater Fish: A Systematic Review of Data Availability for Applications of the MesoHABSIM Model
The MesoHABitat SImulation Model (MesoHABSIM) is the preferred method to calculate spatio-temporal variation in the fish habitat availability in Italian rivers. With the aim of improving the applicability of the MesoHABSIM approach in the Italian territory, we carried out a systematic review of physical habitat preferences for 31 freshwater fish species and three freshwater lampreys, representing 75% of the total indigenous freshwater fish community of Italy. Information related to suitable ranges of depth, flow velocity, biotic/abiotic substrates, covers/shelters was collected and summarized for two critical life stages (adult and juvenile) and two bioperiods (rearing/growth and spawning). Overall, 250 publications were reviewed, classified as 206 peer-reviewed papers, 20 books, 7 PhD thesis, and 17 grey literature sources. Our analysis revealed substantial deficits of information about habitat requirements for more than 30% of Italian freshwater fish species. This information is particularly scarce for the most threatened endemic species, especially for their most critical bioperiod (i.e., spawning). With the aim of preserving freshwater fish biodiversity as required in the EU Biodiversity Strategy for 2030 (European Commission, 2020), accurate information on physical habitat requirements for spawning is crucial. As an example application of MesoHABSIM, the collected habitat preference information was used to define and apply mesohabitat suitability criteria for one fish species (Telestes muticellus) in a regulated river reach of Argentina Creek (Province of Imperia, Italy). This analysis demonstrates the potential for applying information from the current review to other fish species
u-RANIA: a neutron detector based on \mu -RWELL technology
In the framework of the ATTRACT-uRANIA project, funded by the European
Community, we are developing an innovative neutron imaging detector based on
micro-Resistive WELL ( -RWELL) technology. The -RWELL, based on the
resistive detector concept, ensuring an efficient spark quenching mechanism, is
a highly reliable device. It is composed by two main elements: a readout-PCB
and a cathode. The amplification stage for this device is embedded in the
readout board through a resistive layer realized by means of an industrial
process with DLC (Diamond-Like Carbon). A thin layer of BC on the copper
surface of the cathode allows the thermal neutrons detection through the
release of Li and particles in the active volume. This technology
has been developed to be an efficient and convenient alternative to the He
shortage. The goal of the project is to prove the feasibility of such a novel
neutron detector by developing and testing small planar prototypes with readout
boards suitably segmented with strip or pad read out, equipped with existing
electronics or readout in current mode. Preliminary results from the test with
different prototypes, showing a good agreement with the simulation, will be
presented together with construction details of the prototypes and the future
steps of the project.Comment: Prepared for the INSTR20 Conference Proceeding for JINS
A model to explain angular distributions of and decays into and
BESIII data show a particular angular distribution for the decay of the
and mesons into the hyperons
and . More in details the angular distribution of
the decay exhibits an opposite trend
with respect to that of the other three channels: , and
. We define a model to explain the
origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics
The Straw Tube Trackers of the PANDA Experiment
The PANDA experiment will be built at the FAIR facility at Darmstadt
(Germany) to perform accurate tests of the strong interaction through bar pp
and bar pA annihilation's studies. To track charged particles, two systems
consisting of a set of planar, closed-packed, self-supporting straw tube layers
are under construction. The PANDA straw tubes will have also unique
characteristics in term of material budget and performance. They consist of
very thin mylar-aluminized cathodes which are made self-supporting by means of
the operation gas-mixture over-pressure. This solution allows to reduce at
maximum the weight of the mechanical support frame and hence the detector
material budget. The PANDA straw tube central tracker will not only reconstruct
charged particle trajectories, but also will help in low momentum (< 1 GeV)
particle identification via dE/dx measurements. This is a quite new approach
that PANDA tracking group has first tested with detailed Monte Carlo
simulations, and then with experimental tests of detector prototypes. This
paper addresses the design issues of the PANDA straw tube trackers and the
performance obtained in prototype tests.Comment: 7 pages,16 figure
- …