Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised protons

Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise. © 2015

COMPASS-II : COMPASS Future Programs

The COMPASS (COmmon Muon and Proton apparatus for Structure and Spectroscopy) experiment started more than 10 years ago and has published many results concerning nucleon structure and hadron spectroscopy. We propose additional measurements for a new fascinating QCD-related studies of nucleon structure and hadron spectroscopy with small modifications of the present apparatus, that includes either an unpolarized or polarized target

COMPASS polarized Drell-Yan experiment

The COMPASS II started at 2012 that includes polarized Drell-Yan program with a polarized solid target. The availability of pion beam provides an access to the Drell-Yan physics throughout the process where quark(target)-antiquark(beam) pair annihilates electromagnetically with a production of dilepton pair. Study of angular dependencies of the Drell-Yan process cross-section allows us to access to parton distribution functions (PDFs) or, more precisely, a convolutions of various PDFs. The transversely polarized target together with negative pion beam is an important feature of the COMPASS Drell-Yan experiment, that provides us with unique data on transverse momentum dependent (TMD) PDFs. After a plot run in 2014, the experiment has just started in 2015. The role of the Drell-Yan experiment at COMPASS in TMD PDFs study, with a comparison to semi-inclusive deep inelastic scattering experiment, is described. The experimental set-up, the status of the data taking in 2015 and preliminary analysis results in the 2014 run are presented. XVIth

Future plannings for the COMPASS polarized target

The COMPASS collaboration performed a polarized Drell-Yan program to measure TMD (Transverse Momentum Dependent) and PDFs (Parton Distribution Functions) in 2015. We will carry out the program for one more year in 2018 to improve the statistics. In the Drell-Yan program a negative pion beam of 190 GeV/c with an intensity of $10^8$ /s will be scattered on a transversely polarized proton target with a length of 110 cm. We also plan to use a transversely polarized deuteron target for SIDIS (Semi-Inclusive-Deep-Inelastic-Scattering) program with muon beam in 2021 just after a long shut down of the CERN accelerators. We will present the improved COMPASS PT system for the 2018 run and present the future plan of the deuteron target in 2021

Operational experience with the combined solenoid/dipole magnet system of the COMPASS Experiment at CERN

The first ever polarized Drell-Yan measurements were performed at the COMPASS experiment at CERN in 2015, making use of a transversely polarized ammonia target using Dynamic Nuclear Polarization (DNP). A 2.5T longitudinal field is generated with a superconducting solenoid coil carrying a nominal current of 650A, while high homogeneity is obtained by using additional shim - and compensation coils. A superconducting dipole coil encloses the solenoid and together they are integrated in a common cryostat. To obtain transverse polarization, the target material is first polarized in the stronger longitudinal solenoid field and after that, it is rotated to the less strong transverse dipole field (0.63T at 590A). The absolute field strength is never allowed to drop below 0.48T to guarantee a high polarization percentage. In the meantime the forces between the coils should be limited and therefore, the coils cannot both be carrying the nominal operational current, since this will destroy the system. The magnetic field rotation procedure is therefore uniquely developed for this system. The total system is slightly over 2m in length and the stored energy of the system is 2.58MJ for the solenoid at 650A and 0.468MJ for the dipole at 590A.Polarized Drell–Yan measurements require a strong homogeneous magnetic field. A 2.5 T longitudinal field is generated with a superconducting solenoid carrying a nominal current of 650 A, while high homogeneity is obtained by using additional shim—and compensation coils. Since the target needs to be transversely polarized, a second main coil is required. A superconducting dipole coil encloses the solenoid and together they are integrated in a common cryostat. Field rotation, from longitudinal to transverse and vice versa, is possible by simultaneously powering both coils. During the complete procedure, the absolute field strength is never allowed to drop below 0.48 T to guarantee a high polarization percentage. In the meantime, the forces between the coils need to be controlled, and therefore the coils cannot both be carrying the nominal operational current, since this will destroy the system. The magnetic field rotation procedure is therefore uniquely developed for this system. In this paper, the magnet system is described and a summary of the operational experience gained during data taking is provided

Polarized target at COMPASS

The transversely polarized solid proton target was used in 2015 and 2018 for the polarized Drell- Yan experiment at the first in the world with a 10$^8$ /s intensity of 190 GeV pion beam at COM- PASS. Because of the radiation damage, the deterioration of the proton relaxation time of NH$_3$ was observed over more than 6 months data taking period. The radiation also affected the cryogenics control system in 2015. The radiation shield was improved and any incidents on the ra- diation was not observed in 2018. The transversely polarized deuteron target will be applied in 2021 with a muon beam of 160 GeV for Transversity and Sivers parton distribution functions measurements. A cooling test of the polarized target system will be performed in 2020

Search for exclusive photoproduction of Z(c)(+/-) (3900) at COMPASS

A search for the exclusive production of the Z(c)(+/-)(3900) hadron by virtual photons has been performed in the channel Z(c)(+/-)(3900). J/Psi pi(+/-). The data cover the range from 7GeV to 19GeV in the centre-of- mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio BR(Z(c)(+/-)(3900)-> J/Psi pi(+/-)) x sigma(gamma N) -> Z(c)(+/-)(3900) N/sigma gamma N -> J/Psi N 3.7 x10(-3) has been established at the confidence level of90%. (C) 2015 The Authors. Published by Elsevier B.V.CERN managemen

Spin alignment and violation of the OZI rule in exclusive omega and phi production in pp collisions

Exclusive production of the isoscalar vector mesons omega and phi is measured with a 190 GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable x(F) of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass M-pV of the system formed by fast proton p(fast) and vector meson V is discussed in terms of diffractive production of p(fast) V resonances in competition with central production. The measurement of the spin density matrix element rho(00) of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on x(F) and on M-pV are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to omega production which are absent in the case of the phi meson. Removing the low-mass M-pV resonant region, the OZI rule is found to be violated by a factor of eight, independently of x(F). (C) 2014 CERN for the benefit of the COMPASS Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).DFG [1102]; ICTP programme for Training and Research in Italian Laboratories (TRIL); German Bundesministerium fur Bildung und Forschung; Czech Republic MEYS Grants [ME492, LA242]; SAIL (CSR), Govt. of India; CERN-RFBR Grants [08-02-91009, 12-02-91500]; Portuguese FCT - Fundacao para a Ciencia e Tecnologia [CERN/FP/109323/2009, CERN/FP/116376/2010, CERN/FP/123600/2011]; MEXT; JSPS [18002006, 20540299, 18540281]; Daiko Foundation; Yamada Foundation; DFG cluster of excellence 'Origin and Structure of the Universe'; EU FP7 (HadronPhysics3) [283286]; Israel Science Foundation; Polish NCN Grant [DEC-2011/01/M/ST2/02350