COMPASS Status Report 2008

An overview of the 2007 COMPASS run with muon beam is given. The new physics results released during the last year are shortly described. The status of preparation of the 2008 run with hadron beam is discussed

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

Abstract: We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. KCL-PH-TH/2019-65, CERN-TH-2019-12

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

Future Plans of COMPASS

for the COMPASS Collaboration A proposal to the CERN scientific committees concerning COMPASS future plans is being prepared. A request for SPS muon beam delivery in the medium term for precision measurements on the transverse and longitudinal spin structure of the nucleon was submitted. The proposals to study the Generalised Parton Distribution functions via measurements of Deeply Virtual Compton Scattering and the Transverse Momentum Dependent distributions via measurements of the Drell–Yan process are outlined

Mesure de la polarisation des gluons par l'asymétrie de spin dans la production de mésons charmés

L'EXPERIENCE COMPASS VISE PRINCIPALEMENT A MESURER LA POLARISATION DES GLUONS PAR L'ASYMETRIE DE SPIN DANS LA DIFFUSION D'UN FAISCEAU DE MUONS POLARISES SUR UNE CIBLE DE NUCLEONS POLARISES. LE PROCESSUS SENSIBLE A LA DISTRIBUTION DES GLUONS EST LA FUSION PHOTON-GLUON, LAQUELLE PEUT ETRE IDENTIFIEE PAR LA PRODUCTION DE MESONS CHARMES. CE PROCESSUS RESTE TOUTEFOIS RARE ET DIFFICILE A IDENTIFIER DANS UN BRUIT DE FOND IMPORTANT. LA DETERMINATION DE L'EFFICACITE ET DE LA RESOLUTION SPATIALE DES TROIS STATIONS DE CHAMBRES A DERIVE DU SPECTROMETRE PERMET DE S'ASSURER DES BONNES PERFORMANCES DE LA RECONSTRUCTION DES TRAJECTOIRES DES PARTICULES. L'IDENTIFICATION DES HADRONS, ESSENTIELLE DANS LA RECONSTRUCTION DE LA DECROISSANCE DES MESONS CHARMES, EST ASSUREE PAR UN DETECTEUR RICH. EN VUE D'AMELIORER LES PERFORMANCES DE CE DERNIER, UNE METHODE DE TRAITEMENT PROBABILISTE DU SIGNAL ET DU BRUIT A ETE DEVELOPPEE, DE MEME QU'UN PROJET DE REMPLACEMENT DE L'ELECTRONIQUE DE LECTURE. LA DEUXIEME PARTIE DES TRAVAUX EST CONSACREE A LA MESURE DE L'ASYMETRIE D'HELICITE POUR L'EXTRACTION DE LA POLARISATION DES GLUONS. CELA NECESSITE LE DEVELOPPEMENT DE CRITERES DE SELECTION POUR MINIMISER LE RAPPORT BRUIT SUR SIGNAL, ET DE TECHNIQUES DE PONDERATION DES EVENEMENTS PERMETTANT DE REDUIRE L'ERREUR STATISTIQUE. CETTE THESE PRESENTE UN RESULTAT PRELIMINAIRE, BASE SUR LA STATISTIQUE ACCUMULEE PAR COMPASS ENTRE 2002 ET 2004. CECI MET EN EVIDENCE UNE POLARISATION DES GLUONS COMPATIBLE AVEC ZERO, LA BARRE D'ERREUR STATISTIQUE RESTANT NEAMOINS ENCORE ASSEZ IMPORTANTE. LE RESULTAT, QUOIQU'EN ACCORD AVEC LES MESURES EXISTANTES, DEMEURE ENCORE INSUFFISANT POUR TRANCHER ENTRE LES DIFFERENTS MODELES THEORIQUES.THE MAIN AIM OF THE COMPASS EXPERIMENT IS THE MEASUREMENT OF THE GLUON POLARIZATION IN THE NUCLEON, WHICH CAN BE ACCESSED BY THE SPIN ASYMETRY IN THE SCATTERING OF A POLARIZED MUON BEAM ON A POLARIZED NUCLEON TARGET. THE PROCESS SENSITIVE TO THE GLUON DISTRIBUTION IS THE PHOTON-GLUON FUSION, WHICH CAN BE TAGGED BY LOOKING AT THE PRODUCTION OF CHARMED MESONS, HOWEVER IT IS A RARE PROCESS, DOMINATED BY A LARGE BACKGROUND. THE MEASUREMENT OF THE EFFICIENCY AND THE SPACE RESOLUTION OF THE THREE DRIFT CHAMBER STATIONS OF THE SPECTROMETER IS A NECESSARY STEP IN UNDERSTANDING THE PERFORMANCES OF THE RECONSTRUCTION OF PARTICLE TRAJECTORIES. THE HADRON IDENTIFICATION, WHICH IS FUNDAMENTAL IN THE RECONSTRUCTION OF CHARMED MESON DECAY, IS PERFORMED BY A RICH. A STATISTICAL TREATEMENT OF SIGNAL AND BAKGROUND, TOGETHER WITH AN UPGRADE PROJECT TO REPLACE THE PRESENT FRONT END ELECTRONICS, HAVE BEEN DEVELOPPED IN ORDER TO INCREASE THE IDENTIFICATION PERFORMANCES. THE SECOND PART OF THIS WORK CONCERNS THE SPIN ASYMMETRY MEASUREMENT, WHICH REQUIRES THE APPLICATION OF SELECTION CRITERIA IN ORDER TO MINIMIZE THE NOISE OVER SIGNAL RATIO, AND THE DEVELOPMENT OF EVENT-WEIGHTING METHODS TO REDUCE THE STATISTICAL ERROR. ALTHOUGH THE ERROR BARS ARE STILL LARGE, THIS WORK PRESENTS A PRELIMINARY RESULT, BASED ON 2002-2004 STATISTICS, LEADING TO A GLUON POLARIZATION COMPATIBLE WITH ZERO. THE COMPARISON WITH NLO-QCD FITS AND WITH OTHER DIRECT MEASUREMENTS SHOWS THAT THIS RESULT IS COMPATIBLE WITH THE EXISTING MEASUREMENTS BUT, GIVEN THE PRESENT ACCURACY, IT DOES NOT ALLOW TO DISTINGUISH BETWEEN DIFFERENT MODELS.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Caractérisation des micromégas et mesure de la polarisation des gluons sur COMPASS

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF