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Papers by simonetta liuti
AIP Conference Proceedings
Particles produced in non-central relativistic heavy ion collisions could become globally polariz... more Particles produced in non-central relativistic heavy ion collisions could become globally polarized due to the initial large orbital angular momentum and QCD spin-orbital coupling. Measurements of the polarization w.r.t. various kinematic planes may give insight into the mechanisms by which the polarization arises. We report the polarization measurements of Lambda(Lambda), and spin alignment of K* and phi w.r.t. the reaction
AIP Conference Proceedings
ABSTRACT We have developed a 200 keV polarized electron source for generating high bunch charge o... more ABSTRACT We have developed a 200 keV polarized electron source for generating high bunch charge of >3.2 nC within ∼1 ns bunch duration for the International Linear Collider (ILC) and >7.7 pC within 30 ps bunch duration for a basic source study of an Energy Recovery Linac (ERL). In order to improve gun operation voltage and an operational lifetime, we have employed new electrode materials of molybdenum and titanium to eliminate field emission dark current, and restructured a beam transport vacuum systems. As a beam generation for the ERL, bunch charge of up to 28 pC was generated by irradiating with sliced laser pulse trains. The details are described in this report.
AIP Conference Proceedings, 2009
ABSTRACT Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams fo... more ABSTRACT Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams for polarized gas targets and polarized ion sources. Although they have been used for decades the understanding of the beam formation processes is crude. Models were used more or less successfully to describe the measured intensity and beam parameters. ABS's are also foreseen for future experiments, such as PAX [1]. An increase of intensity at a high polarization would be beneficial. A direct simulation Monte-Carlo method (DSMC) [2] was used to describe the beam formation of a hydrogen or deuterium beam in an ABS. For the first time a simulation of a supersonic gas expansion on a molecular level for this application was performed. Beam profile and Time-of-Flight measurements confirmed the simulation results. Furthermore a new method of beam formation was tested, the Carrier Jet method [3], based on an expanded beam surrounded by an over-expanded carrier jet.
AIP Conference Proceedings, 2009
ABSTRACT One of the main goals of the RHIC spin program is to determine the contribution of gluon... more ABSTRACT One of the main goals of the RHIC spin program is to determine the contribution of gluons to the proton spin. At RHIC energies, heavy quark (charm and beauty) production is expected to be dominated by gluon-gluon interactions, so a measurement of the double longitudinal spin asymmetry ALL in heavy quark production in polarized p+p collisions directly probes the polarized gluon distribution inside the proton. We present the latest results on an ALL measurement for J/Ψ and open charm production measured by the PHENIX detector.
AIP Conference Proceedings, 2009
AIP Conference Proceedings, 2009
The injector of the superconducting Darmstadt electron linear accelerator S-DALINAC will soon be ... more The injector of the superconducting Darmstadt electron linear accelerator S-DALINAC will soon be extended by a source of polarized electrons. A test set-up of the future source consists of a 100 keV GaAs polarized gun and associated beamline including an assembly for polarization manipulation and determination. We give a short overview of the existing and planned polarimeters at the different accelerator sites, introduce briefly the future implementation of the polarized source at the S-DALINAC and list experiments that are planned with polarized electron and photon beams.
AIP Conference Proceedings, 2009
ABSTRACT An RF photoinjector with a superconducting cavity (SRF gun) for installation at the Radi... more ABSTRACT An RF photoinjector with a superconducting cavity (SRF gun) for installation at the Radiation Source ELBE was developed within a collaboration of BESSY, DESY, FZD, and MBI. This new and promising injector type allows CW operation and has the potential for the production of high-brightness electron beams. The gun cryostat, the electron diagnostic beamline, and the driver laser with optical beamline were installed. In November 2007 the first beam was produced. Results of the beam parameter measurements with Cs2Te photo cathodes are presented.
AIP Conference Proceedings, 2009
Polarized 3He obtained from metastability exchange optical pumping is used for various double pol... more Polarized 3He obtained from metastability exchange optical pumping is used for various double polarized experiments at the Mainz Microtron (MAMI). At the experimental area more than 70% initial target polarization is available. Besides a description of the target setup and its performance under electron beam conditions, the status of the polarized 3He target for the tagged photon beam at MAMI will be given.
AIP Conference Proceedings, 2009
Study of the Lambda and Lambda hyperon production in the HERMES experiment is discussed. The data... more Study of the Lambda and Lambda hyperon production in the HERMES experiment is discussed. The data were collected using a 27.6 GeV longitudinally polarized positron (or electron) beam of the HERA accelerator and a polarized or unpolarized target. The transverse polarizations (perpendicular to the production plane) of the Lambda and Lambda hyperons have been measured. The spin transfer KLL from the longitudinally polarized target has been found for inclusively detected Lambda and Lambda events. Longitudinal spin transfer DLL from the beam to the Lambda hyperon in the deep inelastic scattering regime has been analyzed. The DLL for Lambda has been measured for the first time.
The European Physical Journal A, 2016
AIP Conference Proceedings, 2009
We propose a Parton Distribution Function (PDF) fitting technique which is based on an interactiv... more We propose a Parton Distribution Function (PDF) fitting technique which is based on an interactive neural network algorithm using Self-Organizing Maps (SOMs). SOMs are visualization algorithms based on competitive learning among spatially-ordered neurons. Our SOMs are trained with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are selected as a seed for the subsequent iteration. Our main goal is thus to provide a fitting procedure that, at variance with the global analyses and standard neural network approaches, allows for an increased control of the systematic bias by enabling user interaction in the various stages of the fitting process.
AIP Conference Proceedings, 2009
ABSTRACT We construct the ERBL region of the unpolarized Generalized Parton Distributions using t... more ABSTRACT We construct the ERBL region of the unpolarized Generalized Parton Distributions using the phenomenological constraints obtained from recent measurements of the ep-->e'gammap reaction, from the nucleon form factor data, and from deep inelastic inclusive measurements.
AIP Conference Proceedings, 2009
ABSTRACT To investigate the spectator role of the 1g{sub 5/2} unpaired proton outside the Z = 50 ... more ABSTRACT To investigate the spectator role of the 1g{sub 5/2} unpaired proton outside the Z = 50 closed shell, the {sup 120}Sn(p-vector,alpha){sup 117}In and {sup 121}Sb(p-vector,alpha){sup 118}Sn reactions have been measured in high resolution experiments at 23 MeV incident proton energy of the Munich MP Tandem accelerator, using the Stern-Gerlach type polarized hydrogen ion source and the Q3D magnetic spectrograph.
Using a physically motivated parameterization based on the reggeized diquark model we perform a f... more Using a physically motivated parameterization based on the reggeized diquark model we perform a flavor separation of the chiral-odd generalized parton distributions obtained from both π 0 and η exclusive electroproduction. In our approach we exploit a connection between the chiral-even and chiral-odd reduced helicity amplitudes using Parity transformations that are relevant for a class of models that includes two-component models. We compare our results for η production to the previously obtained π 0 results, and we make predictions for the transverse single spin asymmetry components which will be measured within the Jefferson Lab 12 GeV program.
In most experiments aimed at determining the masses and mixing parameters for neutrino oscillatio... more In most experiments aimed at determining the masses and mixing parameters for neutrino oscillations in different energy regimes there are strong backgrounds to neutrino interactions with matter that can confuse the expected small signals. One particular set of backgrounds is due to neutrino production of mesons, particularly pions, from nucleon or nuclear targets. It is especially important and theoretically interesting in itself to study coherent neutrino production of pions, i.e. wherein the target does not break up. Preserving the target requires that the meson produced in the reaction will be charged for Charged Current (CC) interactions or neutral for Neutral Current (NC) interactions. Coherent scattering is the weak analog of exclusive neutral meson electroproduction for which considerable progress has been made in understanding the intermediate energy, small momentum transfer region by applying the Generalized Parton Distribution (GPD) phenomenology. The GPD perspective will be explained with emphasis on how the understanding gained from electroproduction of neutral pions can carry over to the neutrino processes.
Aps April Meeting Abstracts, Apr 1, 2006
We present a connection between the modifications induced by the nuclear medium of the nucleon fo... more We present a connection between the modifications induced by the nuclear medium of the nucleon form factors and of the deep inelastic structure functions, obtained using the concept of generalized parton distributions. Generalized parton distributions allow us to access elements of the partonic structure that are common to both the hard inclusive and exclusive scattering processes in nuclei. PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p An important question that remains currently unsolved in Quantum Chromodynamics (QCD), is the determination of the quark and gluon structure of nuclei. Theoretical efforts have so far concentrated on two apparently distinct areas. Many studies were dedicated on one side to pinning down the mechanisms producing nuclear medium modifications of quark and gluon momentum distributions from inclusive (and semi-inclusive) deep inelastic scattering experiments. Sizable A-dependent effects have in fact been observed during the past two decades (see the review in Ref.
AIP Conference Proceedings
Particles produced in non-central relativistic heavy ion collisions could become globally polariz... more Particles produced in non-central relativistic heavy ion collisions could become globally polarized due to the initial large orbital angular momentum and QCD spin-orbital coupling. Measurements of the polarization w.r.t. various kinematic planes may give insight into the mechanisms by which the polarization arises. We report the polarization measurements of Lambda(Lambda), and spin alignment of K* and phi w.r.t. the reaction
AIP Conference Proceedings
ABSTRACT We have developed a 200 keV polarized electron source for generating high bunch charge o... more ABSTRACT We have developed a 200 keV polarized electron source for generating high bunch charge of >3.2 nC within ∼1 ns bunch duration for the International Linear Collider (ILC) and >7.7 pC within 30 ps bunch duration for a basic source study of an Energy Recovery Linac (ERL). In order to improve gun operation voltage and an operational lifetime, we have employed new electrode materials of molybdenum and titanium to eliminate field emission dark current, and restructured a beam transport vacuum systems. As a beam generation for the ERL, bunch charge of up to 28 pC was generated by irradiating with sliced laser pulse trains. The details are described in this report.
AIP Conference Proceedings, 2009
ABSTRACT Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams fo... more ABSTRACT Atomic beam sources (ABS) are widely used workhorses producing polarized atomic beams for polarized gas targets and polarized ion sources. Although they have been used for decades the understanding of the beam formation processes is crude. Models were used more or less successfully to describe the measured intensity and beam parameters. ABS's are also foreseen for future experiments, such as PAX [1]. An increase of intensity at a high polarization would be beneficial. A direct simulation Monte-Carlo method (DSMC) [2] was used to describe the beam formation of a hydrogen or deuterium beam in an ABS. For the first time a simulation of a supersonic gas expansion on a molecular level for this application was performed. Beam profile and Time-of-Flight measurements confirmed the simulation results. Furthermore a new method of beam formation was tested, the Carrier Jet method [3], based on an expanded beam surrounded by an over-expanded carrier jet.
AIP Conference Proceedings, 2009
ABSTRACT One of the main goals of the RHIC spin program is to determine the contribution of gluon... more ABSTRACT One of the main goals of the RHIC spin program is to determine the contribution of gluons to the proton spin. At RHIC energies, heavy quark (charm and beauty) production is expected to be dominated by gluon-gluon interactions, so a measurement of the double longitudinal spin asymmetry ALL in heavy quark production in polarized p+p collisions directly probes the polarized gluon distribution inside the proton. We present the latest results on an ALL measurement for J/Ψ and open charm production measured by the PHENIX detector.
AIP Conference Proceedings, 2009
AIP Conference Proceedings, 2009
The injector of the superconducting Darmstadt electron linear accelerator S-DALINAC will soon be ... more The injector of the superconducting Darmstadt electron linear accelerator S-DALINAC will soon be extended by a source of polarized electrons. A test set-up of the future source consists of a 100 keV GaAs polarized gun and associated beamline including an assembly for polarization manipulation and determination. We give a short overview of the existing and planned polarimeters at the different accelerator sites, introduce briefly the future implementation of the polarized source at the S-DALINAC and list experiments that are planned with polarized electron and photon beams.
AIP Conference Proceedings, 2009
ABSTRACT An RF photoinjector with a superconducting cavity (SRF gun) for installation at the Radi... more ABSTRACT An RF photoinjector with a superconducting cavity (SRF gun) for installation at the Radiation Source ELBE was developed within a collaboration of BESSY, DESY, FZD, and MBI. This new and promising injector type allows CW operation and has the potential for the production of high-brightness electron beams. The gun cryostat, the electron diagnostic beamline, and the driver laser with optical beamline were installed. In November 2007 the first beam was produced. Results of the beam parameter measurements with Cs2Te photo cathodes are presented.
AIP Conference Proceedings, 2009
Polarized 3He obtained from metastability exchange optical pumping is used for various double pol... more Polarized 3He obtained from metastability exchange optical pumping is used for various double polarized experiments at the Mainz Microtron (MAMI). At the experimental area more than 70% initial target polarization is available. Besides a description of the target setup and its performance under electron beam conditions, the status of the polarized 3He target for the tagged photon beam at MAMI will be given.
AIP Conference Proceedings, 2009
Study of the Lambda and Lambda hyperon production in the HERMES experiment is discussed. The data... more Study of the Lambda and Lambda hyperon production in the HERMES experiment is discussed. The data were collected using a 27.6 GeV longitudinally polarized positron (or electron) beam of the HERA accelerator and a polarized or unpolarized target. The transverse polarizations (perpendicular to the production plane) of the Lambda and Lambda hyperons have been measured. The spin transfer KLL from the longitudinally polarized target has been found for inclusively detected Lambda and Lambda events. Longitudinal spin transfer DLL from the beam to the Lambda hyperon in the deep inelastic scattering regime has been analyzed. The DLL for Lambda has been measured for the first time.
The European Physical Journal A, 2016
AIP Conference Proceedings, 2009
We propose a Parton Distribution Function (PDF) fitting technique which is based on an interactiv... more We propose a Parton Distribution Function (PDF) fitting technique which is based on an interactive neural network algorithm using Self-Organizing Maps (SOMs). SOMs are visualization algorithms based on competitive learning among spatially-ordered neurons. Our SOMs are trained with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are selected as a seed for the subsequent iteration. Our main goal is thus to provide a fitting procedure that, at variance with the global analyses and standard neural network approaches, allows for an increased control of the systematic bias by enabling user interaction in the various stages of the fitting process.
AIP Conference Proceedings, 2009
ABSTRACT We construct the ERBL region of the unpolarized Generalized Parton Distributions using t... more ABSTRACT We construct the ERBL region of the unpolarized Generalized Parton Distributions using the phenomenological constraints obtained from recent measurements of the ep-->e'gammap reaction, from the nucleon form factor data, and from deep inelastic inclusive measurements.
AIP Conference Proceedings, 2009
ABSTRACT To investigate the spectator role of the 1g{sub 5/2} unpaired proton outside the Z = 50 ... more ABSTRACT To investigate the spectator role of the 1g{sub 5/2} unpaired proton outside the Z = 50 closed shell, the {sup 120}Sn(p-vector,alpha){sup 117}In and {sup 121}Sb(p-vector,alpha){sup 118}Sn reactions have been measured in high resolution experiments at 23 MeV incident proton energy of the Munich MP Tandem accelerator, using the Stern-Gerlach type polarized hydrogen ion source and the Q3D magnetic spectrograph.
Using a physically motivated parameterization based on the reggeized diquark model we perform a f... more Using a physically motivated parameterization based on the reggeized diquark model we perform a flavor separation of the chiral-odd generalized parton distributions obtained from both π 0 and η exclusive electroproduction. In our approach we exploit a connection between the chiral-even and chiral-odd reduced helicity amplitudes using Parity transformations that are relevant for a class of models that includes two-component models. We compare our results for η production to the previously obtained π 0 results, and we make predictions for the transverse single spin asymmetry components which will be measured within the Jefferson Lab 12 GeV program.
In most experiments aimed at determining the masses and mixing parameters for neutrino oscillatio... more In most experiments aimed at determining the masses and mixing parameters for neutrino oscillations in different energy regimes there are strong backgrounds to neutrino interactions with matter that can confuse the expected small signals. One particular set of backgrounds is due to neutrino production of mesons, particularly pions, from nucleon or nuclear targets. It is especially important and theoretically interesting in itself to study coherent neutrino production of pions, i.e. wherein the target does not break up. Preserving the target requires that the meson produced in the reaction will be charged for Charged Current (CC) interactions or neutral for Neutral Current (NC) interactions. Coherent scattering is the weak analog of exclusive neutral meson electroproduction for which considerable progress has been made in understanding the intermediate energy, small momentum transfer region by applying the Generalized Parton Distribution (GPD) phenomenology. The GPD perspective will be explained with emphasis on how the understanding gained from electroproduction of neutral pions can carry over to the neutrino processes.
Aps April Meeting Abstracts, Apr 1, 2006
We present a connection between the modifications induced by the nuclear medium of the nucleon fo... more We present a connection between the modifications induced by the nuclear medium of the nucleon form factors and of the deep inelastic structure functions, obtained using the concept of generalized parton distributions. Generalized parton distributions allow us to access elements of the partonic structure that are common to both the hard inclusive and exclusive scattering processes in nuclei. PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p An important question that remains currently unsolved in Quantum Chromodynamics (QCD), is the determination of the quark and gluon structure of nuclei. Theoretical efforts have so far concentrated on two apparently distinct areas. Many studies were dedicated on one side to pinning down the mechanisms producing nuclear medium modifications of quark and gluon momentum distributions from inclusive (and semi-inclusive) deep inelastic scattering experiments. Sizable A-dependent effects have in fact been observed during the past two decades (see the review in Ref.