Development of a GEM-TPC prototype

The use of GEM foils for the amplification stage of a TPC instead of a con- ventional MWPC allows one to bypass the necessity of gating, as the backdrift is suppressed thanks to the asymmetric field configuration. This way, a novel continuously running TPC, which represents one option for the PANDA central tracker, can be realized. A medium sized prototype with a diameter of 300 mm and a length of 600 mm will be tested inside the FOPI spectrometer at GSI using a carbon or lithium beam at intermediate energies (E = 1-3AGeV). This detector test under realistic experimental conditions should allow us to verify the spatial resolution for single tracks and the reconstruction capability for displaced vertexes. A series of physics measurement implying pion beams is scheduled with the FOPI spectrometer together with the GEM-TPC as well.Comment: 5 pages, 4 figures, Proceedings for 11th ICATTP conference in como (italy

Production of inclusive ϒ(1S) and ϒ(2S) in p–Pb collisions at √sNN = 5.02 TeV

We report on the production of inclusive Υ(1S) and Υ(2S) in p-Pb collisions at sNN−−−√=5.02 TeV at the LHC. The measurement is performed with the ALICE detector at backward (−4.46<ycms<−2.96) and forward (2.03<ycms<3.53) rapidity down to zero transverse momentum. The production cross sections of the Υ(1S) and Υ(2S) are presented, as well as the nuclear modification factor and the ratio of the forward to backward yields of Υ(1S). A suppression of the inclusive Υ(1S) yield in p-Pb collisions with respect to the yield from pp collisions scaled by the number of binary nucleon-nucleon collisions is observed at forward rapidity but not at backward rapidity. The results are compared to theoretical model calculations including nuclear shadowing or partonic energy loss effects

Inclusive photon production at forward rapidities in proton-proton collisions at s\sqrt{s} = 0.9, 2.76 and 7 TeV

The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities ($2.3 < \eta < 3.9$) in proton-proton collisions at three center-of-mass energies, $\sqrt{s}=0.9$, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2% $\pm$ 0.3% (stat) $\pm$ 8.8% (sys) and 61.2% $\pm$ 0.3% (stat) $\pm$ 7.6% (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities ( $2.3 < \eta < 3.9$ ) in proton–proton collisions at three center-of-mass energies, $\sqrt{s}$   $=$ 0.9, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2 $\pm$ 0.3 % (stat) $\pm$ 8.8 % (sys) and 61.2 $\pm$ 0.3 % (stat) $\pm$ 7.6 % (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range.The multiplicity and pseudorapidity distributions of inclusive photons have been measured at forward rapidities ($2.3 < \eta < 3.9$) in proton-proton collisions at three center-of-mass energies, $\sqrt{s}=0.9$, 2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2% $\pm$ 0.3% (stat) $\pm$ 8.8% (sys) and 61.2% $\pm$ 0.3% (stat) $\pm$ 7.6% (sys), respectively. The photon multiplicity distributions for all center-of-mass energies are well described by negative binomial distributions. The multiplicity distributions are also presented in terms of KNO variables. The results are compared to model predictions, which are found in general to underestimate the data at large photon multiplicities, in particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been explored with the data, but is not observed in the measured pseudorapidity range

Performance of the ALICE Experiment at the CERN LHC

ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables.ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables.ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables

Measurement of quarkonium production at forward rapidity in pppp collisions at s=7\sqrt{s} = 7 TeV

The inclusive production cross sections at forward rapidity of J/$\psi$, $\psi$(2S), $\Upsilon$(1S) and $\Upsilon$(2S) are measured in pp collisions at $\sqrt{s}$ = 7 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb$^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the $\mu^+\mu^-$ invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum $p_T$ and rapidity y, over the transverse momentum range 0 < $p_T$ < 20 GeV/c for J/$\psi$ and 0 < $p_T$ < 12 GeV/c for all other resonances and for 2.5 < y < 4. The measured cross sections integrated over $p_T$ and y, and assuming unpolarized quarkonia, are: $\sigma_{J/\psi}$=6.69 $\pm$ 0.04 $\pm$ 0.61 $\mu$ b, $\sigma_{\psi(2S)}$ = 1.13 $\pm$ 0.07 $\pm$ 0.14 $\mu$b, $\sigma_{\Upsilon(1S)}$ = 54.2 $\pm$ 5.0 $\pm$ 6.7 nb and $\sigma_{\Upsilon(2S)}$=18.4 $\pm$ 3.7 $\pm$ 2.2 nb, where the first uncertainty is statistical and the second one is systematic. These cross sections are obtained assuming unpolarized quarkonium production. The results are compared to measurements performed by other LHC experiments and to theoretical models.The inclusive production cross sections at forward rapidity of J/$\psi$, $\psi$(2S), $\Upsilon$(1S) and $\Upsilon$(2S) are measured in pp collisions at $\sqrt{s} = 7$ TeV with the ALICE detector at the LHC. The analysis is based in a data sample corresponding to an integrated luminosity of 1.35 pb$^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the $\mu^+\mu^-$ invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum $p_{\rm T}$ and rapidity $y$, over the ranges $0 < p_{\rm T} < 20$ GeV/$c$ for J/$\psi$, $0 < p_{\rm T} < 12$ GeV/$c$ for all other resonances and for $2.5 < y < 4$. The measured cross sections integrated over $p_{\rm T}$ and $y$, and assuming unpolarized quarkonia, are: $\sigma_{J/\psi} = 6.69 \pm 0.04 \pm 0.63$ $\mu$b, $\sigma_{\psi^{\prime}} = 1.13 \pm 0.07 \pm 0.14$ $\mu$b, $\sigma_{\Upsilon{\rm(1S)}} = 54.2 \pm 5.0 \pm 6.7$ nb and $\sigma_{\Upsilon{\rm (2S)}} = 18.4 \pm 3.7 \pm 2.2$ nb, where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models.The inclusive production cross sections at forward rapidity of ${\mathrm{J}/\psi }$ , ${\psi (\mathrm{2S})}$ , $\Upsilon$ (1S) and $\Upsilon$ (2S) are measured in $\mathrm{pp}$ collisions at $\sqrt{s}=7~\mathrm{TeV}$ with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb$^{-1}$ . Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the $\mu ^+\mu ^-$ invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum ${p_\mathrm{T}}$ and rapidity $y$ , over the ranges $0<{p_\mathrm{T}}<20$  GeV/c for ${\mathrm{J}/\psi }$ , $0<{p_\mathrm{T}}<12$  GeV/c for all other resonances and for $2.5<y<4$ . The measured cross sections integrated over ${p_\mathrm{T}}$ and $y$ , and assuming unpolarized quarkonia, are: $\sigma _\mathrm{{\mathrm{J}/\psi }}=6.69\pm 0.04\pm 0.63$   \upmu b, $\sigma _{\psi (\mathrm{2S})}=1.13\pm 0.07\pm 0.19$   \upmu b, $\sigma _{\Upsilon (\mathrm{1S})}=54.2\,\pm \, 5.0\pm 6.7$  nb and $\sigma _{\Upsilon (\mathrm{2S})}=18.4\,\pm \,3.7\,\pm \, 2.9$  nb, where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models

Measurement of visible cross sections in proton-lead collisions at sqrt(sNN) = 5.02 TeV in van der Meer scans with the ALICE detector

In 2013, the Large Hadron Collider provided proton-lead and lead-proton collisions at the center-of-mass energy per nucleon pair sqrt(sNN) = 5.02 TeV. Van der Meer scans were performed for both configurations of colliding beams, and the cross section was measured for two reference processes, based on particle detection by the T0 and V0 detectors, with pseudo-rapidity coverage 4.6 < eta< 4.9, -3.3 < eta < -3.0 and 2.8 < eta < 5.1, -3.7 < eta < -1.7, respectively. Given the asymmetric detector acceptance, the cross section was measured separately for the two configurations. The measured visible cross sections are used to calculate the integrated luminosity of the proton-lead and lead-proton data samples, and to indirectly measure the cross section for a third, configuration-independent, reference process, based on neutron detection by the Zero Degree Calorimeters

Exclusive J/ψ\mathrm{J/}\psi photoproduction off protons in ultra-peripheral p-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}}=5.02 TeV

We present the first measurement at the LHC of exclusive J/$\psi$ photoproduction off protons, in ultra-peripheral proton-lead collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5We present the first measurement at the LHC of exclusive J/ψ photoproduction off protons, in ultraperipheral proton-lead collisions at sNN=5.02  TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5<y<4 (p-Pb) or -3.6<y<-2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections σ(γ+p→J/ψ+p) are 33.2±2.2(stat)±3.2(syst)±0.7(theor)  nb in p-Pb and 284±36(stat)-32+27(syst)±26(theor)  nb in Pb-p collisions. We measure this process up to about 700 GeV in the γp center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/ψ photoproduction cross section in γp energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between ∼2×10-2 and ∼2×10-5, thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.We present the first measurement at the LHC of exclusive J/\psi$photoproduction off protons, in ultra-peripheral proton-lead collisions at$\sqrt{s_{\rm NN}}=5.02$TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame,$2.5<y<4$(p-Pb) or$-3.6<y<-2.6$(Pb--p), and no other particles observed in the ALICE acceptance. The measured cross sections$\sigma (\gamma + {\rm p} \rightarrow J/\psi + {\rm p})$are 33.2$\pm$2.2 (stat)$\pm$3.1 (syst)$\pm$0.7 (theo) nb in p-Pb and 284$\pm$36 (stat)$^{+27}_{-32}$(syst)$\pm$26 (theo) nb in Pb-p collisions. We measure this process up to about 700 GeV in the$\gamma {\rm p}$centre-of-mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the$J/\psi$photoproduction cross section in$\gamma {\rm p}$energies from about 20 to 700 GeV, or equivalently, from Bjorken-$x$between$\sim 2\times 10^{-2}$to$\sim 2\times 10^{-5}$, thus indicating no significant change in the gluon density behaviour of the proton between HERA and LHC energies