arXiv subjects

M. Battaglieri

Publications and source records attributed to M. Battaglieri.

156 records · Page 9Linked to original sources

arXiv2006

Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments

Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasi-elastic peak up to the invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous measurements of the proton structure function F2 and cover a similar two-dimensional region of Q2 and Bjorken variable x. Determination of the deuteron F2 over a large x interval including the quasi-elastic peak as a function of Q2, together with the other world data, permit a direct evaluation of the structure function moments for the first time. By fitting the Q2 evolution of these moments with an OPE-based twist expansion we have obtained a separation of the leading twist and higher twist terms. The observed Q2 behaviour of the higher twist contribution suggests a partial cancellation of different higher twists entering into the expansion with opposite signs. This cancellation, found also in the proton moments, is a manifestation of the "duality" phenomenon in the F2 structure function.

hep-ex↗

arXiv2005

Search for $Θ^+(1540)$ pentaquark in high statistics measurement of $γp \to \bar K^0 K^+ n$ at CLAS

The exclusive reaction $γp \to \bar K^0 K^+ n$ was studied in the photon energy range between 1.6-3.8 GeV searching for evidence of the exotic baryon $Θ^+(1540)\to nK^+$. The decay to $nK^+$ requires the assignment of strangeness $S=+1$ to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 $pb^{-1}$. No evidence for the $Θ^+$ pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and $nK^+$ mass. The 95% CL upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.

hep-ex↗

arXiv2005

The deuteron structure function F2 with CLAS

The inclusive, inelastic eD scattering cross section has been measured with the CLAS detector in Hall B of the Thomas Jefferson National Accelerator Facility (TJNAF). Combining these data and previously measured world data we have extracted Nachtmann moments of the deuteron structure function F2 in the region 0.4 < Q2 < 100 GeV2/c2. These results are published in hep-ex/0506004. The purpose of the present CLAS-Note is to tabulate the CLAS deuteron F2 data. A description of the data analysis is reported in hep-ex/0506004.

hep-ex↗

arXiv2004

The CLAS Electromagnetic Calorimeter at Large Angles

The study of the response of the two modules of the large-angle electromagnetic shower calorimeter (LAC) of the CLAS detector to charged and neutral particles is reported. The results agree very well with the Monte Carlo simulation. The procedures adopted for the energy and timing calibration are also discussed, proving that the module geometry allows for simple self-calibrating energy and timing algorithms.

nucl-ex↗

arXiv2003

Measurement of $ep \to e^{'}pπ^{+}π^{-}$: experimental procedures and baryon resonance analysis

The cross section for the reaction $ e p \to e^{\prime} p π^{+} π^{-}$ was measured in the resonance region for 1.4$<$W$<$2.1 GeV and 0.5$<Q^{2}<$1.5 GeV$^{2}$/c$^{2}$ using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on $N^{*}$ and $Δ$ states shows an evident discrepancy. A better description of the data is obtained either by a sizeable change of the properties of the $P_{13}$(1720) resonance or by introducing a new baryon state, not reported in published analyses.

hep-ex↗

arXiv2003

The proton structure function F2 in the resonance region

Unique measurement of the proton structure function F2 in a wide two-dimensional region of x and Q**2 has been reported. The accessible kinematics covers entire resonance region up to W=2.5 GeV in the Q**2 interval from 0.1 to 4.5 GeV**2. Obtained data allowed for the first time an evaluation of moments of the structure function F2 directly from experimental data as well as an intensive study of the Bloom-Gilman duality phenomenon.

hep-ex↗

arXiv2002

Single Quark Transition Model Analysis of Electromagnetic Nucleon Resonance Transitions in the [70,1-] Supermultiplet

We apply the single quark transition model to resonance transition amplitudes extracted from photo-and electroproduction data. We use experimental data on the S11(1535) and D13(1520) nucleon resonances to extract the amplitudes for the electromagnetic transition from the nucleon ground state to the [70,1-] SU(6)xO(3) supermultiplet, and make predictions for the transition amplitudes of all other states associated with the [70,1-]. We find suprisingly good agreement with the data.

hep-ph↗

arXiv2002

Photoproduction of the $ω$ meson on the proton at large momentum transfer

The differential cross section, $dσ/dt$ for $ω$ meson exclusive photoproduction on the proton above the resonance region ($2.6<W<2.9$ GeV) was measured up to a momentum transfer $-t = 5$ GeV$^2$ using the CLAS detector at Jefferson Laboratory. The $ω$ channel was identified by detecting a proton and $π^+$ in the final state and using the missing mass technique. While the low momentum transfer region shows the typical diffractive pattern expected from Pomeron and Reggeon exchange, at large $-t$ the differential cross section has a flat behavior. This feature can be explained by introducing quark interchange processes in addition to the QCD-inspired two-gluon exchange.

hep-ex↗

arXiv2001

DRAFT: Photoproduction of the $ρ^0$ meson on the proton at large momentum transfer

The differential cross section, $dσ/dt$, for $ρ^0$ meson photoproduction on the proton above the resonance region ($2.6<W<2.9$ GeV) was measured up to a momentum transfer $-t = 5$ GeV$^2$ using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The $ρ^0$ channel was extracted from the measured two charged-pion cross section by fitting the $π^+π^-$ and $pπ^+$ invariant masses. The low momentum transfer region shows the typical diffractive pattern expected from Reggeon-exchange. The flatter behavior at large -t cannot be explained solely in terms of QCD-inspired two-gluon exchange models. The data indicate that other processes, like quark interchange, are important to fully describe $ρ$ photoproduction.

hep-ex↗

arXiv2000

A Phenomenological Description of (π^{-}Δ^{++}) Photo- and Electroproduction in Nucleon Resonance Region

The (π^{-}Δ^{++}) production on the nucleon by real and virtual photons is discussed as initial step in a simple model approach for the two pion photo- and electroproduction on the nucleon, with emphasis on nucleon resonance excitation which is of interest for new facilities like TJNAF. A calculation for (π^{-}Δ^{++}) channel in resonance excitation region is presented and compared to existing experimental data along with a discussion of physical effects that we find to be of relevance. The calculation is proposed as a starting basis for the investigation of (N^{*}) electromagnetic form factors using experimental data about two pion production by real and virtual photons.

hep-ph↗

arXiv1999

Power corrections in the longitudinal and transverse structure functions of proton and deuteron

Power corrections to the Q**2 behaviour of the low-order moments of both the longitudinal and transverse structure functions of proton and deuteron have been investigated using available phenomenological fits of existing data in the Q**2 range between 1 and 20 (GeV/c)**2. The Natchmann definition of the moments has been adopted for disentangling properly target-mass and dynamical higher-twist effects in the data. The leading twist has been treated at next-to-leading order in the strong coupling constant and the effects of higher orders of the perturbative series have been estimated using a renormalon-inspired model. The contributions of (target-dependent) multiparton correlations to both 1/Q**2 and 1/Q**4 power terms have been determined in the transverse channel, while the longitudinal one appears to be consistent with a pure infrared renormalon picture in the whole Q**2-range between 1 and 20 (GeV/c)**2. Finally, the extracted twist-2 contribution in the deuteron turns out to be compatible with the hypothesis of an enhanced d-quark parton distribution at large x.

hep-ph↗

arXiv1996

Quasi-elastic and inelastic inclusive electron scattering from an oxygen jet target

The results of an experiment on inclusive electron scattering from an oxygen jet target, performed in a wide range of energy and momentum transfer covering both quasi-elastic and $Δ$(1232) resonance regions, are reported. In the former region the theoretical predictions, obtained including effects of nucleon-nucleon correlations in both initial and final states, give a good description of the experimental data. In the inelastic region a broadening as well as a damping of the resonant part of the cross section with respect to the free nucleon case is observed. The need of more detailed calculations including nuclear structure effects on the electroproduction cross section of nucleon resonances is highlighted.

nucl-th↗