Speaker
Description
In semi-inclusive deep inelastic scattering (SIDIS) the non-zero transverse momentum of partons is reflected in the transverse momentum $P_T$ of the produced hadrons and in their azimuthal distribution. Assuming Gaussian dependence of transverse momentum dependent (TMD) PDFs and fragmentation functions (FFs) upon quark transverse momentum, exponential distribution of $P_T^2$ is expected. For an unpolarised nucleon, three azimuthal modulations that can be related to combinations of twist-two or higher-twist TMD PDFs and FFs arise: the so-called Cahn effect reflected in a $\cos\phi$ modulation, the $\cos2\phi$ term related to the Boer−Mulders PDF and $\sin\phi$ effect known as beam-spin asymmetry.
In 2016 and 2017, the COMPASS experiment at CERN collected a large sample of SIDIS events using a longitudinally polarised 160 GeV/$c$ muon beam scattering on a liquid hydrogen target. The $P_T^2$ distributions and the amplitudes of the aforementioned azimuthal modulations have been extracted for charged hadrons from part of the data. The $P_T^2$ distributions can be described by two exponentials. The results qualitatively agree with earlier COMPASS measurements with an isoscalar target.
| Submitted on behalf of a Collaboration? | Yes |
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