R. Heitz

Measurement of the cross section for hard exclusive $I ¨ ^{0}$ leptoproduction

M. G. Alexeev, G. D. Alexeev, A. Amoroso +199

We report on a measurement of hard exclusive $I ¨ ^{0}$ muoproduction on the proton by COMPASS using 160 GeV/ $c$ polarised $I^¼^{+}$ and $I^¼^{-}$ beams of the CERN SPS impinging on a liquid…

hep-ex2016

Multiplicities of charged pions and unidentified charged hadrons from deep-inelastic scattering of muons off an isoscalar target

C. Adolph, J. Agarwala, M. Aghasyan +224

Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured in bins of the Bjorken scaling variable $x$ , the relative virtual-photo…

Exclusive $I ¨ $ meson muoproduction on transversely polarised protons

C. Adolph, J. Agarwala, M. Aghasyan +225

Exclusive production of $I ¨ $ mesons was studied at the COMPASS experiment by scattering $160 GeV / c$ muons off transversely polarised protons. Five single-spin and…

hep-ex2020

Antiproton over proton and K $^{-}$ over K $^{+}$ multiplicity ratios at high $z$ in DIS

M. G. Alexeev, G. D. Alexeev, A. Amoroso +195

The $p ˉ$ over p multiplicity ratio is measured in deep-inelastic scattering for the first time using (anti-) protons carrying a large fraction of the virtual-photon energ…

Measurement of $P_{T}$ -weighted Sivers asymmetries in leptoproduction of hadrons

M. G. Alexeev, G. D. Alexeev, A. Amoroso +209

The transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron transverse momentum $P_{T}$ , allow for the extraction of importan…

Light isovector resonances in $I ¨ ^{-} p \to I ¨ ^{-} I ¨ ^{-} I ¨ ^{+} p$ at 190 GeV/ $c$

M. Aghasyan, M. G. Alexeev, G. D. Alexeev +221

We have performed the most comprehensive resonance-model fit of $I ¨ ^{-} I ¨ ^{-} I ¨ ^{+}$ states using the results of our previously published partial-wave analysis (PWA) of a large data set…

First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process

Aghasyan, R. Akhunzyanov, M. G. Alexeev +216

The first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan (DY) process is reported. We use the CERN SPS 190 GeV/ $c$ , $I ¨ ^{-}$ beam and…

hep-ex2022

The exotic meson $I ¨ _{1} (1600)$ with $J^{P C} = 1^{-+}$ and its decay into $I ¨ (770) I ¨ $

M. G. Alexeev, G. D. Alexeev, A. Amoroso +192

We study the spin-exotic $J^{P C} = 1^{-+}$ amplitude in single-diffractive dissociation of 190 GeV $/ c$ pions into $I ¨ ^{-} I ¨ ^{-} I ¨ ^{+}$ using a hydrogen target and confirm the $Ï_1(1600)…

Sivers asymmetry extracted in SIDIS at the hard scale of the Drell-Yan process at COMPASS

C. Adolph, M. Aghasyan, R. Akhunzyanov +223

Proton transverse-spin azimuthal asymmetries are extracted from the COMPASS 2010 semi-inclusive hadron measurements in deep inelastic muon-nucleon scattering in those four regions…

Contribution of exclusive diffractive processes to the measured azimuthal asymmetries in SIDIS

J. Agarwala, M. G. Alexeev, G. D. Alexeev +203

Hadron leptoproduction in Semi-Inclusive measurements of Deep-Inelastic Scattering (SIDIS) on unpolarised nucleons allows one to get information on the intrinsic transverse momentu…

Letter of Intent: A New QCD facility at the M2 beam line of the CERN SPS (COMPASS++/AMBER)

B. Adams, C. A. Aidala, R. Akhunzyanov +263

A New QCD facility at the M2 beam line of the CERN SPS COMPASS++/AMBER

hep-ex2023

Final COMPASS results on the transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan process

G. D. Alexeev, M. G. Alexeev, C. Alice +180

The COMPASS Collaboration performed measurements of the Drell-Yan process in 2015 and 2018 using a 190 GeV/c $I ¨ ^{-}$ beam impinging on a transversely polarised ammonia target. Com…

Transverse Extension of Partons in the Proton probed by Deeply Virtual Compton Scattering

R. Akhunzyanov, M. G. Alexeev, G. D. Alexeev +223

We report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/ $c$ polarized $I^¼^{+}$ and $I^¼^{-}$ beams of the CERN SPS impinging o…

Leading-order determination of the gluon polarisation from semi-inclusive deep inelastic scattering data

C. Adolph, M. Aghasyan, R. Akhunzyanov +217

Using a novel analysis technique, the gluon polarisation in the nucleon is re-evaluated using the longitudinal double-spin asymmetry measured in the cross section of semi-inclusive…

K $^{-}$ over K $^{+}$ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy

R. Akhunzyanov, M. G. Alexeev, G. D. Alexeev +207

The K $^{-}$ over K $^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The d…

Transverse-momentum-dependent Multiplicities of Charged Hadrons in Muon-Deuteron Deep Inelastic Scattering

M. Aghasyan, R. Akhunzyanov, M. G. Alexeev +227

A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaborat…

Azimuthal asymmetries of charged hadrons produced in high-energy muon scattering off longitudinally polarised deuterons

C. Adolph, M. Aghasyan, R. Akhunzyanov +221

Single hadron azimuthal asymmetries of positive and negative hadrons produced in muon semi-inclusive deep inelastic scattering off longitudinally polarised deuterons are determined…

hep-ex2016

Final COMPASS results on the deuteron spin-dependent structure function $g_{1}^{d}$ and the Bjorken sum rule

C. Adolph, M. Aghasyan, R. Akhunzyanov +223

Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a $^{6}$ LiD target. The data were t…

hep-ex2016

Multiplicities of charged kaons from deep-inelastic muon scattering off an isoscalar target

C. Adolph, J. Agarwala, M. Aghasyan +223

Precise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented in three-dimensional bins of the Bjorken scaling variable…

hep-ex2021

Probing transversity by measuring $I^$ polarisation in SIDIS

M. G. Alexeev, G. D. Alexeev, A. Amoroso +196

Based on the observation of sizeable target-transverse-spin asymmetries in single-hadron and hadron-pair production in Semi-Inclusive measurements of Deep Inelastic Scattering (SID…

Longitudinal double-spin asymmetry $A_{1}^{p}$ and spin-dependent structure function $g_{1}^{p}$ of the proton at small values of $x$ and $Q^{2}$

M. Aghasyan, R. Akhunzyanov, M. G. Alexeev +225

We present a precise measurement of the proton longitudinal double-spin asymmetry $A_{1}^{p}$ and the proton spin-dependent structure function $g_{1}^{p}$ at photon virtualitie…

hep-ph2021

Triangle Singularity as the Origin of the $a_{1} (1420)$

G. D. Alexeev, M. G. Alexeev, A. Amoroso +194

The COMPASS experiment recently discovered a new isovector resonance-like signal with axial-vector quantum numbers, the $a_{1} (1420)$ , decaying to $f_{0} (980) I ¨ $ . With a mass too close…

Search for muoproduction of $X (3872)$ at COMPASS and indication of a new state $X (3872)$

M. Aghasyan, R. Akhunzyanov, M. G. Alexeev +224

We have searched for exclusive production of exotic charmonia in the reaction $I^¼^{+} N \to I^¼^{+} (J / I ¨ I ¨ ^{+} I ¨ ^{-}) I ¨ ^{\pm} N^{'}$ using COMPASS data collected with incoming muo…