1,721,164 research outputs found
TMD and spin asymmetries in SIDIS
Get PDFA review of the most recent measurements of leading twist transverse momentum dependent distribution
and fragmentation function accessed in the semi-inclusive deep inelastic scattering HERMES, COMPASS
and JLab experiments is given
Collins and Sivers asymmetries on the deuteron from COMPASS
No full textThe COMPASS experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and on hadron spectroscopy, using muon and hadron beams. One of the main objectives for the spin program with the muon beam is the measurement of the transversity distribution in semi inclusive deep inelastic scattering (SIDIS). In the years 2002, 2003 and 2004 data were collected using a 160 GeV polarized muon beam and a LiD target transversely polarized with respect to the muon beam for about 20% of the running time. Here the results for the Collins and the Sivers asymmetries extracted from the 2002 data are presented together with the projected statistical error for the whole 2002-2004 period and for the proton run foreseen in 2006. Results for polarization from 2002-2003 data are also presented
The COMPASS measurement of the pion polarizability
No full textThe COMPASS experiment at CERN reported in a 2015 Physical Review Letter the first precise measurement of the electromagnetic polarizability of the charged pion. After a short introduction on the experiment, we will underline the basic aspects of the measurement of the polarizability performed by COMPASS and the impact of the result
The COMPASS experiment
No full textThe COMPASS Experiment at the CERN SPS has a broad physics program focused on the study of the spin structure of the nucleon and on hadron spectroscopy. Key measurements for the spin program are the gluon contribution to the spin of the nucleon, semi-inclusive measurements, and the first measurement of the transverse structure function . Its state-of-the-art apparatus consists of a two-stage large acceptance spectrometer designed for high data rates and equipped with high-resolution tracking, particle identification and electromagnetic and hadronic calorimetry. The first year of physics run (2002) was devoted to the spin programme, using a polarised beam at 160 GeV/c and a polarised LiD target
Collins and Sivers asymmetries from COMPASS
No full textIn the years 2002-2004 the COMPASS experiment has collected data with a polarized LiD target and a 160 GeV muon beam. About 20% of the running time has been devoted to measure transverse spin eects in semi inclusive deep inelastic scattering, one of the main objectives of the COMPASS spin program. The results for the Collins and the Sivers asymmetries, both for unidentied and identied hadrons, are presented here. The measured asymmetries on the LiD target are small and compatible with zero within the few percent statistical errors, an important result which can be interpreted as cancellation between u and d quark contribution in the deuteron and which allows to better constrain the parton distribution functions
Azimuthal asymmetries in SIDIS off unpolarized targets at COMPASS
No full textAzimuthal asymmetries measured in unpolarized semi-inclusive deep inelastic scattering bring important information on the inner structure of the nucleons, and can be used both to estimate the average quark transverse momentum k_T and to access the so-far unmeasured Boer-Mulders functions. COMPASS results using part of the 2004 data collected with a 6LiD target and a 160 GeV positive muon beam are presented separately for positive and negative hadrons
Physics Results from COMPASS
No full textThe COMPASS Experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and on hadron spectroscopy, using muon and hadron beams. Main objectives for the spin program with the muon beam are the direct measurement of the gluon contribution to the spin of the nucleon, semi-inclusive measurements, and the measurement of the transverse spin distribution . The COMPASS apparatus consists of a two-stage large acceptance spectrometer designed for high data rates and equipped with high-resolution tracking, particle identification and electromagnetic and hadronic calorimetry. The data taking is ongoing since 2002 and till now was mainly devoted to the spin programme using a 160 GeV naturally polarized, beam and a polarized LiD target. First physics results from the 2002 and 2003 runs are presented.The COMPASS Experiment at the CERN SPS has a broad physics program focused on the nucleon spin structure and on hadron spectroscopy, using muon and hadron beams. Main objectives for the spin program with the muon beam are the direct measurement of the gluon contribution to the spin of the nucleon, semi-inclusive measurements, and the measurement of the transverse spin distribution . The COMPASS apparatus consists of a two-stage large acceptance spectrometer designed for high data rates and equipped with high-resolution tracking, particle identification and electromagnetic and hadronic calorimetry. The data taking is ongoing since 2002 and till now was mainly devoted to the spin programme using a 160 GeV naturally polarized, beam and a polarized \mrf{^6LiD} target. First physics results from the 2002 and 2003 runs are presented
COMPASS Results on Collins and Sivers Asymmetries
No full textIn the list of the main items studied by the CERN COMPASS experiment there are the transverse spin and momentum effects visible in the azimuthal distributions of hadrons produced in the deep inelastic scattering. In the years 2002-2004 COMPASS has collected data with a 6LiD target with the polarization oriented transversely with respect to the muon beam direction for about 20% of the running time; in 2007, COMPASS has used for the first time a proton target with the data taking time equally shared between longitudinal and transverse polarization of the target. After reviewing the results obtained with the deuteron, the new results for the Collins and Sivers asymmetries of the proton will be presented.In the list of the main items studied by the CERN COMPASS experiment there are the transverse spin and momentum effects visible in the azimuthal distributions of hadrons produced in the deep inelastic scattering. In the years 2002-2004 COMPASS has collected data with a 6LiD target with the polarization oriented transversely with respect to the muon beam direction for about 20% of the running time; in 2007, COMPASS has used for the first time a proton NH_3 target with the data taking time equally shared between longitudinal and transverse polarization of the target. After reviewing the results obtained with the deuteron, the new results for the Collins and Sivers asymmetries of the proton will be presented
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