$$\pi ^-p\rightarrow \eta ^{(\prime )}\, \pi ^- p$$ in the double-Regge region

The production of $$\eta ^{(\prime )}\pi $$ η ( ′ ) π pairs constitutes one of the golden channels to search for hybrid exotics, with explicit gluonic degrees of freedom. Understanding the dynamics and backgrounds associated to $$\eta ^{(\prime )}\pi $$ η ( ′ ) π production above the resonance region is required to impose additional constraints to the resonance extraction. We consider the reaction $$\pi ^-p\rightarrow \eta ^{(\prime )} \pi ^- \,p$$ π - p → η ( ′ ) π - p measured by COMPASS. We show that the data in $$2.4< m_{\eta ^{(\prime )}\pi } < 3.0{\mathrm {\,GeV}} $$ 2.4 < m η ( ′ ) π < 3.0 GeV can be described by amplitudes based on double-Regge exchanges. The angular distribution of the meson pairs, in particular in the $$\eta ' \pi $$ η ′ π channel, can be attributed to flavor singlet exchanges, suggesting the presence of a large gluon content that couples strongly to the produced mesons.

Significance of gluon density at soft and hard processes at LHC

We study the role of the non-perturbative input to the transverse momentum dependent (TMD) gluon density in hard processes at the LHC. We derive the TMD gluon distribution from the fit of the inclusive hadron spectra measured at low transverse momenta in [Formula: see text] collisions at the LHC and demonstrate that the best description of these spectra for larger hadron transverse momenta can be achieved by matching the derived TMD gluon distribution with the exact solution of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation obtained at small transverse momenta outside the saturation region. A special attention is put to the phenomenological applications of presented TMD parton densities to some LHC processes, which are sensitive to the quark and gluon content of a proton.

MICROMEGAS TRACKERS FOR HADRONIC PHYSICS

Modern experiments in hadronic physics require excellent detection and tracking capabilities in very high flux environment. Probing the quark and gluon content of the nucleon indeed necessitates semi-inclusive or exclusive reactions with very small cross-sections. Micromegas detectors have therefore been rapidly identified as natural candidates to equip the hottest region of the COMPASS spectrometer at CERN. Benefitting from several years of smooth operation at COMPASS, the Micromegas have been proposed to equip the future central tracker of the CLAS12 experiment at the Jefferson Laboratory. This project triggered an important R&D on the bulk and resistive technologies and inspired several projects involving cylindrical trackers. This paper focuses on the design and performance of the COMPASS and CLAS12 Micromegas, and reviews the R&D made on the discharge reduction in large hadron fluxes.

PARTON DISCRIMINATION USING JETS WITH ALICE AT THE LHC

A Monte Carlo study of two jet observables that can be used to obtain jet samples enhanced in quark or gluon content is presented. We compare the performance of one of these methods on pure Monte Carlo events with that after the transport of events through the full simulation of the ALICE experiment. It is shown that the performance of the method is not deteriorated by experimental effects like resolution and inefficiency.