The production of c and b quarks in γγ collisions is studied with the L3 detector at LEP with 410... more The production of c and b quarks in γγ collisions is studied with the L3 detector at LEP with 410 pb −1 of data, collected at centre-of-mass energies from 189 GeV to 202 GeV. Hadronic final states containing c and b quarks are identified by detecting electrons or muons from their semileptonic decays. The cross sections σ(e + e − → e + e − ccX) and σ(e + e − → e + e − bbX) are measured and compared to nextto-leading order perturbative QCD calculations. The cross section of b production is measured in γγ collisions for the first time. It is in excess of the QCD prediction by a factor of three.
Using the data recorded with the L3 detector at LEP, w e study the process e + e ! + () for event... more Using the data recorded with the L3 detector at LEP, w e study the process e + e ! + () for events with hard initial-state photon radiation. The eective centre-of-mass energies of the muons range from 50 GeV t o 8 6 G e V. The data sample corresponds to an integrated luminosity of 103.5 pb 1 and yields 293 muonpair events with a hard photon along the beam direction. The events are used to determine the cross sections and the forward-backward charge asymmetries at centre-of-mass energies below the Z resonance.
PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galac... more PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10 −8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15 2006 in a 350 × 600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives and the performance in the first months after launch.
The PAMELA experiment aims to measure with great precision the antimatter present in our Galaxy i... more The PAMELA experiment aims to measure with great precision the antimatter present in our Galaxy in the form of high energy particles; in the same time it will measure the galactic, solar and trapped components of cosmic rays. The experiment will be housed on board a Russian Resurs-DK1 satellite and launched in the year 2005 to fly a 350-600 km orbit with an inclination of 70.4°. All operations of the instrument-including data storage-are handled by the PAMELA Storage and Control Unit (PSCU), which is divided in a Central Processing Unit (CPU) and a Mass Memory (MM). The CPU of the experiment is based on a ERC-32 architecture (a SPARC v7 implementation) running a real time operating system (RTEMS). The main purpose of the CPU is to handle slow control, acquire and store data on a 2 GB MM. Communications between PAMELA and the satellite are performed via a 1553B bus. Data acquisition from the sub-detectors (Time-of-Flight counter, Magnetic Spectrometer, Electromagnetic Calorimeter, Anticoincidence shield, Neutron Detector, and Bottom scintillator S4) is performed via a 2 MB/s interface. Download from the PAMELA MM towards the satellite main storage unit is handled by a 16 MB/s bus. The daily amount of data transmitted to ground has been evaluated in not more 20 GB. In this work, we describe the CPU of the experiment and the general software scheme.
We report on a search for R{parity breaking eects due to supersymmetric tau{ sneutrino exchange i... more We report on a search for R{parity breaking eects due to supersymmetric tau{ sneutrino exchange in the reactions e + e ! e + e and e + e ! + at centre{of{ mass energies from 91 GeV to 172 GeV, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward{backward asymmetries for these reactions is found. Upper limits for the couplings 131 and 232 for sneutrino masses up to m 190 GeV are determined from an analysis of the expected eects due to tau sneutrino exchange.
A search for exclusive decays of B 0 d and B 0 s mesons has been performed in the channels B 0 d ... more A search for exclusive decays of B 0 d and B 0 s mesons has been performed in the channels B 0 d ! J; B 0 s !J; B 0 d !J 0 and B 0 s ! J 0. The data sample consisted of more than three and half million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90% condence level: 3:2 10 4 on Br(B 0 d ! J 0) and the rst experimental limits: Br(B 0 d ! J) < 1:2 10 3 ; Br(B 0 s ! J) < 3:8 10 3 ; Br(B 0 s ! J 0
The three different helicity states of W ± bosons, produced in the reaction e + e − → W + W − → ν... more The three different helicity states of W ± bosons, produced in the reaction e + e − → W + W − → νqq are studied using leptonic and hadronic W decays at √ s=183 GeV and 189 GeV. The W polarisation is also measured as a function of the scattering angle between the W − and the direction of the e − beam. The analysis demonstrates that W bosons are produced with all three helicities, the longitudinal and the two transverse states. Combining the results from the two center-of-mass energies and with leptonic and hadronic W decays, the fraction of longitudinally polarised W ± bosons is measured to be 0.261 ± 0.051(stat.) ± 0.016(syst.
We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass ener... more We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass energies between 50 GeV and 170 GeV, and 20 GeV and 140 GeV, respectively, using the L3 detector at LEP. The analysis is based on data corresponding to an integrated luminosity of 232:2 p b 1. A total of 2856 radiative Bhabha and 4641 Compton scattering events are collected. Total and dierential cross sections for both reactions are presented and found to bein goodagreement with QED expectations. Our measurement of Compton scattering at the highest energies obtained so far is used to derive exclusion limits on the coupling for the on-shell production of an excited electron e ? decaying into a e pair in the mass range 20 GeV < m e ? < 170 GeV.
The process e + e − → Zγγ → qqγγ is studied in 0.5 fb −1 of data collected with the L3 detector a... more The process e + e − → Zγγ → qqγγ is studied in 0.5 fb −1 of data collected with the L3 detector at centre-of-mass energies between 130.1 GeV and 201.7 GeV. Cross sections are measured and found to be consistent with the Standard Model expectations. The study of the least energetic photon constrains the quartic gauge boson couplings to −0.008 GeV −2 < a 0 /Λ 2 < 0.005 GeV −2 and −0.
We h a v e studied the process e + e !n (n2) at centre-of-mass energies of 161.3 GeV and 172.1 Ge... more We h a v e studied the process e + e !n (n2) at centre-of-mass energies of 161.3 GeV and 172.1 GeV. The analysis is based on a sample of events collected by the L3 detector in 1996 corresponding to total integrated luminosities of 10.7 pb 1 and 10.1 pb 1 respectively. The observed rates of events with two and more photons and the characteristic distributions are in good agreement with the Standard Model expectations. This is used to set lower limits on contact interaction energy scale parameters, on the QED cut-o parameters and on the mass of excited electrons.
The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray a... more The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the galaxy. More precise secondary production models are required for a complete interpretation of the results.
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forwa... more LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward region of LHC collisions. The physics goal is to provide data for calibrating the hadron interaction models that are used in the study of Extremely High-Energy Cosmic-Rays. This is possible since the laboratory equivalent collision energy of LHC is 10 17 eV. Two LHCf detectors, consisting of imaging calorimeters made of tungsten plates, plastic scintillator and position sensitive sensors, are installed at zero degree collision angle ±140 m from an interaction point (IP). Although the lateral dimensions of these calorimeters are very compact, ranging from 20 mm×20 mm to 40 mm×40 mm, the energy resolution is expected to be better than 6% and the position resolution better than 0.2 mm for γ-rays with energy from 100 GeV to 7 TeV. This has been confirmed by test beam results at the CERN SPS. These calorimeters can measure particles emitted in the pseudo rapidity range η>8.4. Detectors, data acquisition and electronics are optimized to operate during the early phase of the LHC commissioning with luminosity below 10 30 cm −2 s −1. LHCf is expected to obtain data to compare with the major hadron interaction models within a week or so of operation at luminosity ∼ 10 29 cm −2 s −1. After ∼10 days of operation at luminosity ∼10 29 cm −2 s −1 , the light output of the plastic scintillators is expected to degrade by ∼10% due to radiation damage. This degradation will be monitored and corrected for using calibration pulses from a laser.
LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forwa... more LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward region of LHC collisions. The physics goal is to provide data for calibrating the hadron interaction models that are used in the study of Extremely High-Energy Cosmic-Rays. This is possible since the laboratory equivalent collision energy of LHC is 10 17 eV. Two LHCf detectors, consisting of imaging calorimeters made of tungsten plates, plastic scintillator and position sensitive sensors, are installed at zero degree collision angle ±140 m from an interaction point (IP). Although the lateral dimensions of these calorimeters are very compact, ranging from 20 mm×20 mm to 40 mm×40 mm, the energy resolution is expected to be better than 6% and the position resolution better than 0.2 mm for γ-rays with energy from 100 GeV to 7 TeV. This has been confirmed by test beam results at the CERN SPS. These calorimeters can measure particles emitted in the pseudo rapidity range η>8.4. Detectors, data acquisition and electronics are optimized to operate during the early phase of the LHC commissioning with luminosity below 10 30 cm −2 s −1. LHCf is expected to obtain data to compare with the major hadron interaction models within a week or so of operation at luminosity ∼ 10 29 cm −2 s −1. After ∼10 days of operation at luminosity ∼10 29 cm −2 s −1 , the light output of the plastic scintillators is expected to degrade by ∼10% due to radiation damage. This degradation will be monitored and corrected for using calibration pulses from a laser.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers wer... more ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers were measured at the SPS H4 beam line in 2007 using electron beams of 50–200 GeV and muon beams of 150 GeV. The absolute energy scale was determined in these data. The results that were obtained (&lt;5%&lt;5% energy resolution) are well understood by using Monte Carlo simulations and are good enough for the requirements of the LHCf experiment.
Bulletin of the Russian Academy of Sciences: Physics, 2011
The generally accepted theory explaining the observed cosmological baryon asymmetry involves mech... more The generally accepted theory explaining the observed cosmological baryon asymmetry involves mechanisms of baryosynthesis that generate asymmetry in an initially baryon symmetric Universe. Due to the possible inhomogeneous spatial nature of such mechanisms, antimatter domains could arise in the Universe. This hypothesis can be tested by the direct measurement of fluxes of antinuclei in cosmic rays. Searching for antihelium nuclei is therefore among the objectives of the PAMELA experiment. We analyzed data from August 2006 to December 2009 and obtained a preliminary value for the upper limit of the antihelium/helium flux ratio that could lead to some restrictions on the existing theoretical models of the production and prop agation of antimatter in the Galaxy.
Bulletin of the Russian Academy of Sciences: Physics, 2011
The generally accepted theory explaining the observed cosmological baryon asymmetry involves mech... more The generally accepted theory explaining the observed cosmological baryon asymmetry involves mechanisms of baryosynthesis that generate asymmetry in an initially baryon symmetric Universe. Due to the possible inhomogeneous spatial nature of such mechanisms, antimatter domains could arise in the Universe. This hypothesis can be tested by the direct measurement of fluxes of antinuclei in cosmic rays. Searching for antihelium nuclei is therefore among the objectives of the PAMELA experiment. We analyzed data from August 2006 to December 2009 and obtained a preliminary value for the upper limit of the antihelium/helium flux ratio that could lead to some restrictions on the existing theoretical models of the production and prop agation of antimatter in the Galaxy.
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers wer... more ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers were measured at the SPS H4 beam line in 2007 using electron beams of 50–200 GeV and muon beams of 150 GeV. The absolute energy scale was determined in these data. The results that were obtained (&lt;5%&lt;5% energy resolution) are well understood by using Monte Carlo simulations and are good enough for the requirements of the LHCf experiment.
The production of c and b quarks in γγ collisions is studied with the L3 detector at LEP with 410... more The production of c and b quarks in γγ collisions is studied with the L3 detector at LEP with 410 pb −1 of data, collected at centre-of-mass energies from 189 GeV to 202 GeV. Hadronic final states containing c and b quarks are identified by detecting electrons or muons from their semileptonic decays. The cross sections σ(e + e − → e + e − ccX) and σ(e + e − → e + e − bbX) are measured and compared to nextto-leading order perturbative QCD calculations. The cross section of b production is measured in γγ collisions for the first time. It is in excess of the QCD prediction by a factor of three.
Using the data recorded with the L3 detector at LEP, w e study the process e + e ! + () for event... more Using the data recorded with the L3 detector at LEP, w e study the process e + e ! + () for events with hard initial-state photon radiation. The eective centre-of-mass energies of the muons range from 50 GeV t o 8 6 G e V. The data sample corresponds to an integrated luminosity of 103.5 pb 1 and yields 293 muonpair events with a hard photon along the beam direction. The events are used to determine the cross sections and the forward-backward charge asymmetries at centre-of-mass energies below the Z resonance.
PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galac... more PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range (protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10 −8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15 2006 in a 350 × 600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives and the performance in the first months after launch.
The PAMELA experiment aims to measure with great precision the antimatter present in our Galaxy i... more The PAMELA experiment aims to measure with great precision the antimatter present in our Galaxy in the form of high energy particles; in the same time it will measure the galactic, solar and trapped components of cosmic rays. The experiment will be housed on board a Russian Resurs-DK1 satellite and launched in the year 2005 to fly a 350-600 km orbit with an inclination of 70.4°. All operations of the instrument-including data storage-are handled by the PAMELA Storage and Control Unit (PSCU), which is divided in a Central Processing Unit (CPU) and a Mass Memory (MM). The CPU of the experiment is based on a ERC-32 architecture (a SPARC v7 implementation) running a real time operating system (RTEMS). The main purpose of the CPU is to handle slow control, acquire and store data on a 2 GB MM. Communications between PAMELA and the satellite are performed via a 1553B bus. Data acquisition from the sub-detectors (Time-of-Flight counter, Magnetic Spectrometer, Electromagnetic Calorimeter, Anticoincidence shield, Neutron Detector, and Bottom scintillator S4) is performed via a 2 MB/s interface. Download from the PAMELA MM towards the satellite main storage unit is handled by a 16 MB/s bus. The daily amount of data transmitted to ground has been evaluated in not more 20 GB. In this work, we describe the CPU of the experiment and the general software scheme.
We report on a search for R{parity breaking eects due to supersymmetric tau{ sneutrino exchange i... more We report on a search for R{parity breaking eects due to supersymmetric tau{ sneutrino exchange in the reactions e + e ! e + e and e + e ! + at centre{of{ mass energies from 91 GeV to 172 GeV, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward{backward asymmetries for these reactions is found. Upper limits for the couplings 131 and 232 for sneutrino masses up to m 190 GeV are determined from an analysis of the expected eects due to tau sneutrino exchange.
A search for exclusive decays of B 0 d and B 0 s mesons has been performed in the channels B 0 d ... more A search for exclusive decays of B 0 d and B 0 s mesons has been performed in the channels B 0 d ! J; B 0 s !J; B 0 d !J 0 and B 0 s ! J 0. The data sample consisted of more than three and half million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1995. No candidate events have been observed for any of the modes thus determining upper limits at 90% condence level: 3:2 10 4 on Br(B 0 d ! J 0) and the rst experimental limits: Br(B 0 d ! J) < 1:2 10 3 ; Br(B 0 s ! J) < 3:8 10 3 ; Br(B 0 s ! J 0
The three different helicity states of W ± bosons, produced in the reaction e + e − → W + W − → ν... more The three different helicity states of W ± bosons, produced in the reaction e + e − → W + W − → νqq are studied using leptonic and hadronic W decays at √ s=183 GeV and 189 GeV. The W polarisation is also measured as a function of the scattering angle between the W − and the direction of the e − beam. The analysis demonstrates that W bosons are produced with all three helicities, the longitudinal and the two transverse states. Combining the results from the two center-of-mass energies and with leptonic and hadronic W decays, the fraction of longitudinally polarised W ± bosons is measured to be 0.261 ± 0.051(stat.) ± 0.016(syst.
We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass ener... more We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass energies between 50 GeV and 170 GeV, and 20 GeV and 140 GeV, respectively, using the L3 detector at LEP. The analysis is based on data corresponding to an integrated luminosity of 232:2 p b 1. A total of 2856 radiative Bhabha and 4641 Compton scattering events are collected. Total and dierential cross sections for both reactions are presented and found to bein goodagreement with QED expectations. Our measurement of Compton scattering at the highest energies obtained so far is used to derive exclusion limits on the coupling for the on-shell production of an excited electron e ? decaying into a e pair in the mass range 20 GeV < m e ? < 170 GeV.
The process e + e − → Zγγ → qqγγ is studied in 0.5 fb −1 of data collected with the L3 detector a... more The process e + e − → Zγγ → qqγγ is studied in 0.5 fb −1 of data collected with the L3 detector at centre-of-mass energies between 130.1 GeV and 201.7 GeV. Cross sections are measured and found to be consistent with the Standard Model expectations. The study of the least energetic photon constrains the quartic gauge boson couplings to −0.008 GeV −2 < a 0 /Λ 2 < 0.005 GeV −2 and −0.
We h a v e studied the process e + e !n (n2) at centre-of-mass energies of 161.3 GeV and 172.1 Ge... more We h a v e studied the process e + e !n (n2) at centre-of-mass energies of 161.3 GeV and 172.1 GeV. The analysis is based on a sample of events collected by the L3 detector in 1996 corresponding to total integrated luminosities of 10.7 pb 1 and 10.1 pb 1 respectively. The observed rates of events with two and more photons and the characteristic distributions are in good agreement with the Standard Model expectations. This is used to set lower limits on contact interaction energy scale parameters, on the QED cut-o parameters and on the mass of excited electrons.
The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray a... more The satellite-borne experiment PAMELA has been used to make a new measurement of the cosmic-ray antiproton flux and the antiproton-to-proton flux ratio which extends previously published measurements down to 60 MeV and up to 180 GeV in kinetic energy. During 850 days of data acquisition approximately 1500 antiprotons were observed. The measurements are consistent with purely secondary production of antiprotons in the galaxy. More precise secondary production models are required for a complete interpretation of the results.
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forwa... more LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward region of LHC collisions. The physics goal is to provide data for calibrating the hadron interaction models that are used in the study of Extremely High-Energy Cosmic-Rays. This is possible since the laboratory equivalent collision energy of LHC is 10 17 eV. Two LHCf detectors, consisting of imaging calorimeters made of tungsten plates, plastic scintillator and position sensitive sensors, are installed at zero degree collision angle ±140 m from an interaction point (IP). Although the lateral dimensions of these calorimeters are very compact, ranging from 20 mm×20 mm to 40 mm×40 mm, the energy resolution is expected to be better than 6% and the position resolution better than 0.2 mm for γ-rays with energy from 100 GeV to 7 TeV. This has been confirmed by test beam results at the CERN SPS. These calorimeters can measure particles emitted in the pseudo rapidity range η>8.4. Detectors, data acquisition and electronics are optimized to operate during the early phase of the LHC commissioning with luminosity below 10 30 cm −2 s −1. LHCf is expected to obtain data to compare with the major hadron interaction models within a week or so of operation at luminosity ∼ 10 29 cm −2 s −1. After ∼10 days of operation at luminosity ∼10 29 cm −2 s −1 , the light output of the plastic scintillators is expected to degrade by ∼10% due to radiation damage. This degradation will be monitored and corrected for using calibration pulses from a laser.
LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forwa... more LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward region of LHC collisions. The physics goal is to provide data for calibrating the hadron interaction models that are used in the study of Extremely High-Energy Cosmic-Rays. This is possible since the laboratory equivalent collision energy of LHC is 10 17 eV. Two LHCf detectors, consisting of imaging calorimeters made of tungsten plates, plastic scintillator and position sensitive sensors, are installed at zero degree collision angle ±140 m from an interaction point (IP). Although the lateral dimensions of these calorimeters are very compact, ranging from 20 mm×20 mm to 40 mm×40 mm, the energy resolution is expected to be better than 6% and the position resolution better than 0.2 mm for γ-rays with energy from 100 GeV to 7 TeV. This has been confirmed by test beam results at the CERN SPS. These calorimeters can measure particles emitted in the pseudo rapidity range η>8.4. Detectors, data acquisition and electronics are optimized to operate during the early phase of the LHC commissioning with luminosity below 10 30 cm −2 s −1. LHCf is expected to obtain data to compare with the major hadron interaction models within a week or so of operation at luminosity ∼ 10 29 cm −2 s −1. After ∼10 days of operation at luminosity ∼10 29 cm −2 s −1 , the light output of the plastic scintillators is expected to degrade by ∼10% due to radiation damage. This degradation will be monitored and corrected for using calibration pulses from a laser.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers wer... more ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers were measured at the SPS H4 beam line in 2007 using electron beams of 50–200 GeV and muon beams of 150 GeV. The absolute energy scale was determined in these data. The results that were obtained (&lt;5%&lt;5% energy resolution) are well understood by using Monte Carlo simulations and are good enough for the requirements of the LHCf experiment.
Bulletin of the Russian Academy of Sciences: Physics, 2011
The generally accepted theory explaining the observed cosmological baryon asymmetry involves mech... more The generally accepted theory explaining the observed cosmological baryon asymmetry involves mechanisms of baryosynthesis that generate asymmetry in an initially baryon symmetric Universe. Due to the possible inhomogeneous spatial nature of such mechanisms, antimatter domains could arise in the Universe. This hypothesis can be tested by the direct measurement of fluxes of antinuclei in cosmic rays. Searching for antihelium nuclei is therefore among the objectives of the PAMELA experiment. We analyzed data from August 2006 to December 2009 and obtained a preliminary value for the upper limit of the antihelium/helium flux ratio that could lead to some restrictions on the existing theoretical models of the production and prop agation of antimatter in the Galaxy.
Bulletin of the Russian Academy of Sciences: Physics, 2011
The generally accepted theory explaining the observed cosmological baryon asymmetry involves mech... more The generally accepted theory explaining the observed cosmological baryon asymmetry involves mechanisms of baryosynthesis that generate asymmetry in an initially baryon symmetric Universe. Due to the possible inhomogeneous spatial nature of such mechanisms, antimatter domains could arise in the Universe. This hypothesis can be tested by the direct measurement of fluxes of antinuclei in cosmic rays. Searching for antihelium nuclei is therefore among the objectives of the PAMELA experiment. We analyzed data from August 2006 to December 2009 and obtained a preliminary value for the upper limit of the antihelium/helium flux ratio that could lead to some restrictions on the existing theoretical models of the production and prop agation of antimatter in the Galaxy.
The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in ... more The pair production of Z bosons is studied using the data collected by the L3 detector at LEP in 1998 in e + e − collisions at a centre-of-mass energy of 189 GeV. All the visible final states are considered and the cross section of this process is measured to be 0.74 +0.15 −0.14 (stat.) ±0.04 (syst.) pb. Final states containing b quarks are enhanced by a dedicated selection and their production cross section is found to be 0.18 +0.09 −0.07 (stat.) ±0.02 (syst.) pb. Both results are in agreement with the Standard Model predictions. Limits on anomalous couplings between neutral gauge bosons are derived from these measurements.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012
ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers wer... more ABSTRACT Energy resolution and linearity of the LHCf calorimeters for electromagnetic showers were measured at the SPS H4 beam line in 2007 using electron beams of 50–200 GeV and muon beams of 150 GeV. The absolute energy scale was determined in these data. The results that were obtained (&lt;5%&lt;5% energy resolution) are well understood by using Monte Carlo simulations and are good enough for the requirements of the LHCf experiment.
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Papers by G. Castellini