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The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

Gaseous detectors are used in high energy physics as trackers or, more generally, as devices for the measurement of the particle position. For this reason, they must provide high spatial resolution and they have to be able to operate in regions of intense radiation, i.e. around the interaction point of collider machines. Among these, Micro Pattern Gaseous Detectors (MPGD) are the latest frontier and allow to overcome many limitations of the pre-existing detectors, such as the radiation tolerance and the rate capability. The gas Electron Multiplier (GEM) is a MPGD that exploits an intense electric field in a reduced amplification region in order to prevent discharges. Several amplification stages, like in a triple-GEM, allow to increase the detector gain and to reduce the discharge probability. Reconstruction techniques such as charge centroid (CC) and micro-Time Projection Chamber (\\(\\upmu\\)TPC) are used to perform the position measurement. From literature triple-GEMs show a stable behaviour up to \\(10^8\\,\\)Hz/cm\\(^2\\). A testbeam with four planar triple-GEMs has been performed at the Mainz Microtron (MAMI) facility and their performance was evaluated in different beam conditions. In this article a focus on the time performance for the \\(\\upmu\\)TPC clusterization is given and a new measurement of the triple-GEM limits at high rate will be presented.

The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few body systems to neutron stars and may also be observable experimentally in two-spin state, ultra-cold atomic gas systems.

We have measured the induced polarization of the \\({\\Lambda}(1116)\\) in the reaction \\(ep\\rightarrow e'K^+{\\Lambda}\\), detecting the scattered \\(e'\\) and \\(K^+\\) in the final state along with the proton from the decay \\(\\Lambda\\rightarrow p\\pi^-\\).The present study used the CEBAF Large Acceptance Spectrometer (CLAS), which allowed for a large kinematic acceptance in invariant energy \\(W\\) (\\(1.6\\leq W \\leq 2.7\\) GeV) and covered the full range of the kaon production angle at an average momentum transfer \\(Q^2=1.90\\) GeV\\(^2\\).In this experiment a 5.50 GeV electron beam was incident upon an unpolarized liquid-hydrogen target. We have mapped out the \\(W\\) and kaon production angle dependencies of the induced polarization and found striking differences from photoproduction data over most of the kinematic range studied. However, we also found that the induced polarization is essentially \\(Q^2\\) independent in our kinematic domain, suggesting that somewhere below the \\(Q^2\\) covered here there must be a strong \\(Q^2\\) dependence. Along with previously published photo- and electroproduction cross sections and polarization observables, these data are needed for the development of models, such as effective field theories, and as input to coupled-channel analyses that can provide evidence of previously unobserved \\(s\\)-channel resonances.

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the \\(\\eta\\) photoproduction reaction \\(\\gamma p \\rightarrow \\eta p\\). Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the J\"ulich model to examine the case for the existence of a narrow \\(N^*\\) resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable using that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.

We present a search for ten baryon-number violating decay modes of \\(\\Lambda\\) hyperons using the CLAS detector at Jefferson Laboratory. Nine of these decay modes result in a single meson and single lepton in the final state (\\(\\Lambda \\rightarrow m \\ell\\)) and conserve either the sum or the difference of baryon and lepton number (\\(B \\pm L\\)). The tenth decay mode (\\(\\Lambda \\rightarrow \\bar{p}\\pi^+\\)) represents a difference in baryon number of two units and no difference in lepton number. We observe no significant signal and set upper limits on the branching fractions of these reactions in the range \\((4-200)\\times 10^{-7}\\) at the \\(90\\%\\) confidence level.

We present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron (\\(^{15}\\)ND\\(_3\\)) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry \\(A_1^d\\) and the polarized structure function \\(g_1^d\\) were extracted over a wide kinematic range (0.05 GeV\\(^2 < Q^2 <\\) 5 GeV\\(^2\\) and 0.9 GeV \\(< W <\\) 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions \\(A_1^n\\) and \\(g_1^n\\) of the (bound) neutron, which are so far unknown in the resonance region, \\(W < 2\\) GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large \\(x\\), a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.

Much less is known about neutron structure than that of the proton due to the absence of free neutron targets. Neutron information is usually extracted from data on nuclear targets such as deuterium, requiring corrections for nuclear binding and nucleon off-shell effects. These corrections are model dependent and have significant uncertainties, especially for large values of the Bjorken scaling variable x. The Barely Off-shell Nucleon Structure (BONuS) experiment at Jefferson Lab measured the inelastic electron deuteron scattering cross section, tagging spectator protons in coincidence with the scattered electrons. This method reduces nuclear binding uncertainties significantly and has allowed for the first time a (nearly) model independent extraction of the neutron structure function. A novel compact radial time projection chamber was built to detect protons with momentum between 70 and 150 MeV/c. For the extraction of the free neutron structure function \\(F_{2n}\\), spectator protons at backward angle and with momenta below 100 MeV/c were selected, ensuring that the scattering took place on a nearly free neutron. The scattered electrons were detected with Jefferson Lab's CLAS spectrometer. The extracted neutron structure function \\(F_{2n}\\) and its ratio to the deuteron structure function \\(F_{2d}\\) are presented in both the resonance and deep inelastic regions. The dependence of the cross section on the spectator proton momentum and angle is investigated, and tests of the spectator mechanism for different kinematics are performed. Our data set can be used to study neutron resonance excitations, test quark hadron duality in the neutron, develop more precise parametrizations of structure functions, as well as investigate binding effects (including possible mechanisms for the nuclear EMC effect) and provide a first glimpse of the asymptotic behavior of d/u as x goes to 1.

Exclusive neutral-pion electroproduction (\\(ep\\to e^\\prime p^\\prime \\pi^0\\)) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections \\(d^4\\sigma/dtdQ^2dx_Bd\\phi_\\pi\\) and structure functions \\(\\sigma_T+\\epsilon\\sigma_L, \\sigma_{TT}\\) and \\(\\sigma_{LT}\\) as functions of \\(t\\) were obtained over a wide range of \\(Q^2\\) and \\(x_B\\). The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found that the inclusion of vector meson rescattering processes is necessary to bring the magnitude of the calculated and measured structure functions into rough agreement. In the handbag framework, there are two independent calculations, both of which appear to roughly explain the magnitude of the structure functions in terms of transversity generalized parton distributions.

Objectives: A case-control study within a cohort of the workers employed by Electricité de France and Gaz de France between 1988 and 1992 was carried out to investigate relationships between cancers and socioeconomic status, including the effects of social mobility, by studying three professional career points. Methods: All the incident cases of breast cancer in women and all the incident cases of upper respiratory and digestive tract cancer (comprising cancers of the larynx, pharynx, buccal cavity and esophagus), lung cancer, hematopoietic system cancers and colon cancer in men were extracted from the Cancer Register of the Social Security Department. The controls were matched for age (men) and for age and length of employment in the company (women). Socioeconomic status was measured at three professional career points (beginning, midpoint (about 35), and time of diagnosis (about 48) by two types of socio-professional variables: employee category (low, medium, high) and a variable based on the French socioeconomic status classification system. An estimation of social mobility was done between career beginning and midpoint. Cases and controls were compared for socioeconomic status at the three career points. They were also compared for social mobility. Results: The differences between the social categories were larger at the start than later in the career for breast cancer in women. The category of operations staff was used as a reference, and this analysis shows a difference between the risks associated with supervisors (OR = 2.0) and managers and specialist professions (OR = 1.5). There were large differences according to the type of cancer in men. A socioeconomic gradient in the incidence of cancers of the upper respiratory and digestive tract was observed at every career stage. The gradient was largest at the moment of diagnosis. The odds ratio was 3.4 for supervisors, 7.8 for operations staff and 14.8 for production staff. There was a socioeconomic gradient in lung cancer at all points in the career and in the incidence of the hematopoietic system cancers at mid-career and at diagnosis. No association between socioeconomic status and colon cancer was found. Social mobility accentuated all these results. Conclusion: Socioeconomic status is involved in the development of cancers. Our study suggests that the transition from social to biological processes could act via specific lifestyle and/or work-related risk factors. When there is a social gradient in the incidence of a cancer, an individual's social change is at least as important as his/her original social status in the relationship between cancer and social class.