Alberto Gago - Profile on Academia.edu (original) (raw)

Papers by Alberto Gago

The European Physical Journal C, 2015

The observation of Higgs decays into heavy neutrinos would be strong evidence for new physics ass... more The observation of Higgs decays into heavy neutrinos would be strong evidence for new physics associated to neutrino masses. In this work we propose a search for such decays within the Type I Seesaw model in the few-GeV mass range via displaced vertices. Using 300 fb −1 of integrated luminosity, at 13 TeV, we explore the region of parameter space where such decays are measurable. We show that, after imposing pseudorapidity cuts, there still exists a region where the number of events is larger than O (10). We also find that conventional triggers can greatly limit the sensitivity of our signal, so we display several relevant kinematical distributions which might aid in the optimization of a dedicated trigger selection.

Resolving Standard and Nonstandard CP Violation Phases in Neutrino Oscillations

AIP Conference Proceedings, 2010

ABSTRACT

Physics Letters B, 2013

In high-energy heavy-ion collisions, the correlations between the emitted particles can be used a... more In high-energy heavy-ion collisions, the correlations between the emitted particles can be used as a probe to gain insight into the charge creation mechanisms. In this Letter, we report the first results of such studies using the electric charge balance function in the relative pseudorapidity (∆η) and azimuthal angle (∆ϕ) in Pb-Pb collisions at √ s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. The width of the balance function decreases with growing centrality (i.e. for more central collisions) in both projections. This centrality dependence is not reproduced by HIJING, while AMPT, a model which incorporates strings and parton rescattering, exhibits qualitative agreement with the measured correlations in ∆ϕ but fails to describe the correlations in ∆η. A thermal blast-wave model incorporating local charge conservation and tuned to describe the p T spectra and v 2 measurements reported by ALICE, is used to fit the centrality dependence of the width of the balance function and to extract the average separation of balancing charges at freeze-out. The comparison of our results with measurements at lower energies reveals an ordering with √ s NN : the balance functions become narrower with increasing energy for all centralities. This is consistent with the effect of larger radial flow at the LHC energies but also with the late stage creation scenario of balancing charges. However, the relative decrease of the balance function widths in ∆η and ∆ϕ with centrality from the highest SPS to the LHC energy exhibits only small differences. This observation cannot be interpreted solely within the framework where the majority of the charge is produced at a later stage in the evolution of the heavy-ion collision.

Physical Review D, 2004

The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kami... more The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kamiokande-I was fit to the variations expected from active two-neutrino oscillations. The best fit in the Large Mixing Angle solution has a mixing angle of tan 2 θ = 0.55 and a mass squared difference of ∆m 2 = 6.3 × 10 −5 eV 2 between the two neutrino mass eigenstates. The fitted day/night asymmetry of −1.8 ± 1.6(stat) +1.3 −1.2 (syst)% has improved statistical precision over previous measurements and agrees well with the expected asymmetry of-2.1%.

Micromaser without the rotating-wave approximation: The Bloch-Siegert shift and related effects

Optics Communications, 1997

The micromaser dynamics is studied without assuming the validity of the rotating-wave approximati... more The micromaser dynamics is studied without assuming the validity of the rotating-wave approximation (RWA). Through numerically evaluating micromaser spectra for first and second order correlations we compare our results with those based on the RWA for both the resonant and the nonresonant case. We find that in the resonant case values of g/ω0 — where g is the atom-field coupling

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

Neutrino interaction events in the MINERνA detector are visually represented with a web-based too... more Neutrino interaction events in the MINERνA detector are visually represented with a web-based tool called Arachne. Data are retrieved from a central server via AJAX, and client-side JavaScript draws images into the user's browser window using the draft HTML 5 standard. These technologies allow neutrino interactions to be viewed by anyone with a web browser, allowing for easy hand-scanning of particle interactions. Arachne has been used in MINERνA to evaluate neutrino data in a prototype detector, to tune reconstruction algorithms, and for public outreach and education.

Use of a Scintillator Detector for Luminosity Measurements

High Energy Physics - Proceedings of the Fifth Latin American Symposium, 2006

One of the main goals of the V0 setup for the ALICE experiment at CERN will be the measurement of... more One of the main goals of the V0 setup for the ALICE experiment at CERN will be the measurement of the instantaneous luminosity passing by the ALICE detector. We study here this possibility and also the efficiency of this setup for different processes of inelastic production. The utility of this setup to reject events not coming for the interaction vertex and to reconstruct this vertex position is discused.

Physics Letters B, 2011

Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at 2.76 Te... more Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in |η| < 0.8 and 0.3 < p T < 20 GeV/c are compared to the expectation in pp collisions at the same √ s NN , scaled by the number of underlying nucleon-nucleon collisions. The comparison is expressed in terms of the nuclear modification factor R AA . The result indicates only weak medium effects (R AA ≈ 0.7) in peripheral collisions. In central collisions, R AA reaches a minimum of about 0.14 at p T = 6-7 GeV/c and increases significantly at larger p T . The measured suppression of high-p T particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb-Pb collisions at the LHC.

Physics Letters B, 2013

The elliptic, v 2 , triangular, v 3 , and quadrangular, v 4 , azimuthal anisotropic flow coeffici... more The elliptic, v 2 , triangular, v 3 , and quadrangular, v 4 , azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions and (anti-)protons in Pb-Pb collisions at √ s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range |η| < 0.8 at different collision centralities and as a function of transverse momentum, p T , out to p T = 20 GeV/c. The observed non-zero elliptic and triangular flow depends only weakly on transverse momentum for p T > 8 GeV/c. The small p T dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to p T = 8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least p T = 8 GeV/c indicating that the particle type dependence persists out to high p T .

Physics Letters B, 2013

Angular correlations between charged trigger and associated particles are measured by the ALICE d... more Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < p T,assoc < p T,trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in highmultiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p T bins, and the widths show no significant evolution with event multiplicity or p T . These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge.

Journal of High Energy Physics, 2012

The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ ... more The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ \sqrt{s}=7 $ TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5.6 nb−1. The fraction of J/ψ from the decay of long-lived beauty hadrons was determined for J/ψ candidates with transverse momentum p t > 1.3 GeV/c and rapidity |y| < 0.9. The cross section for prompt J/ψ mesons, i.e. directly produced J/ψ and prompt decays of heavier charmonium states such as the ψ(2S) and χc resonances, is σprompt J/ψ (p t > 1.3 GeV/c, |y| < 0.9) = 8.3 ± 0.8 (stat.) ± 1.1 (syst.) $ _{-1.4}^{+1.5 } $ (syst. pol.) μb. The cross section for the production of b-hadrons decaying to J/ψ with p t > 1.3 GeV/c and |y| < 0.9 is $ {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} $ (p t > 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.) $ _{-0.32}^{+0.26 } $ (syst.) μb. The results are compared to QCD model predictio...

Journal of High Energy Physics, 2012

We present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ a... more We present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ and 7TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p T,LT in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p T thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2–3 between the lower and higher collision energies, depending on the track p T threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed p T in the Tran...

Physics Letters B, 2012

The ALICE experiment has measured low-mass dimuon production in pp collisions at √ s = 7 TeV in t... more The ALICE experiment has measured low-mass dimuon production in pp collisions at √ s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (η, ρ, ω, η , φ) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for ω and φ are σ ω (1 < p t < 5 GeV/c, 2.5 < y < 4) = 5.28 ± 0.54(stat) ± 0.49(syst) mb and σ φ (1 < p t < 5 GeV/c, 2.5 < y < 4) = 0.940 ± 0.084(stat) ± 0.076(syst) mb. The differential cross sections d 2 σ /dy dp t are extracted as a function of p t for ω and φ. The ratio between the ρ and ω cross section is obtained. Results for the φ are compared with other measurements at the same energy and with predictions by models.

Physics Letters B, 2012

The ALICE Collaboration has measured inclusive J/ψ production in pp collisions at a center of mas... more The ALICE Collaboration has measured inclusive J/ψ production in pp collisions at a center of mass energy √ s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y| < 0.9 and 2.5 < y < 4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L e int = 1.1 nb -1 and L µ int = 19.9 nb -1 , and the corresponding signal statistics are N e + e - J/ψ = 59 ± 11 and N = 1364 ± 53. We present dσ J/ψ /dy for the two rapidity regions under study and, for the forward-y range, d 2 σ J/ψ /dydp t in the transverse momentum domain 0 < p t < 8 GeV/c. The results are compared with previously published results at √ s = 7 TeV and with theoretical calculations. Inclusive J/ψ production in pp collisions at √ s = 2.76 TeV 3

Physics Letters B, 2012

Angular correlations between unidentified charged trigger (t) and associated (a) particles are me... more Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at s NN = 2.76 TeV for transverse momenta 0.25 < p t,a T < 15 GeV/c, where p t T > p a T . The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η| < 1.0. Distributions in relative azimuth φ ≡ φ tφ a are analyzed for | η| ≡ |η tη a | > 0.8, and are referred to as "long-range correlations". Fourier components V n ≡ cos(n φ) are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy V n (p t T , p a T ) is fully described in terms of single-particle anisotropies ). This expectation is tested for 1 n 5 by applying a global fit of all V n (p t T , p a T ) to obtain the best values v n {GF}(p T ). It is found that for 2 n 5, the fit agrees well with data up to p a T ∼ 3-4 GeV/c, with a trend of increasing deviation as p t T and p a T are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25 < p T < 15 GeV/c range using a single v n (p T ) curve; such a description is however approximately possible for 2 n 5 when p a T < 4 GeV/c. For the n = 1 harmonic, however, a single v 1 (p T ) curve is not obtained even within the reduced range p a T < 4 GeV/c.

Physics Letters B, 2010

We h a v e analysed a sample of 2.36 million minimum bias events produced in pp collisions at p s... more We h a v e analysed a sample of 2.36 million minimum bias events produced in pp collisions at p s = 630 GeV in the UA1 experiment at the CERN collider. We h a v e studied production of charged particles with transverse momenta (p T) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of hp T i with charged particle multiplicity m a y be related to changing production of low p T particles.

The European Physical Journal C, 2015

The observation of Higgs decays into heavy neutrinos would be strong evidence for new physics ass... more The observation of Higgs decays into heavy neutrinos would be strong evidence for new physics associated to neutrino masses. In this work we propose a search for such decays within the Type I Seesaw model in the few-GeV mass range via displaced vertices. Using 300 fb −1 of integrated luminosity, at 13 TeV, we explore the region of parameter space where such decays are measurable. We show that, after imposing pseudorapidity cuts, there still exists a region where the number of events is larger than O (10). We also find that conventional triggers can greatly limit the sensitivity of our signal, so we display several relevant kinematical distributions which might aid in the optimization of a dedicated trigger selection.

Resolving Standard and Nonstandard CP Violation Phases in Neutrino Oscillations

AIP Conference Proceedings, 2010

ABSTRACT

Physics Letters B, 2013

In high-energy heavy-ion collisions, the correlations between the emitted particles can be used a... more In high-energy heavy-ion collisions, the correlations between the emitted particles can be used as a probe to gain insight into the charge creation mechanisms. In this Letter, we report the first results of such studies using the electric charge balance function in the relative pseudorapidity (∆η) and azimuthal angle (∆ϕ) in Pb-Pb collisions at √ s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. The width of the balance function decreases with growing centrality (i.e. for more central collisions) in both projections. This centrality dependence is not reproduced by HIJING, while AMPT, a model which incorporates strings and parton rescattering, exhibits qualitative agreement with the measured correlations in ∆ϕ but fails to describe the correlations in ∆η. A thermal blast-wave model incorporating local charge conservation and tuned to describe the p T spectra and v 2 measurements reported by ALICE, is used to fit the centrality dependence of the width of the balance function and to extract the average separation of balancing charges at freeze-out. The comparison of our results with measurements at lower energies reveals an ordering with √ s NN : the balance functions become narrower with increasing energy for all centralities. This is consistent with the effect of larger radial flow at the LHC energies but also with the late stage creation scenario of balancing charges. However, the relative decrease of the balance function widths in ∆η and ∆ϕ with centrality from the highest SPS to the LHC energy exhibits only small differences. This observation cannot be interpreted solely within the framework where the majority of the charge is produced at a later stage in the evolution of the heavy-ion collision.

Physical Review D, 2004

The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kami... more The time variation of the elastic scattering rate of solar neutrinos with electrons in Super-Kamiokande-I was fit to the variations expected from active two-neutrino oscillations. The best fit in the Large Mixing Angle solution has a mixing angle of tan 2 θ = 0.55 and a mass squared difference of ∆m 2 = 6.3 × 10 −5 eV 2 between the two neutrino mass eigenstates. The fitted day/night asymmetry of −1.8 ± 1.6(stat) +1.3 −1.2 (syst)% has improved statistical precision over previous measurements and agrees well with the expected asymmetry of-2.1%.

Micromaser without the rotating-wave approximation: The Bloch-Siegert shift and related effects

Optics Communications, 1997

The micromaser dynamics is studied without assuming the validity of the rotating-wave approximati... more The micromaser dynamics is studied without assuming the validity of the rotating-wave approximation (RWA). Through numerically evaluating micromaser spectra for first and second order correlations we compare our results with those based on the RWA for both the resonant and the nonresonant case. We find that in the resonant case values of g/ω0 — where g is the atom-field coupling

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

Neutrino interaction events in the MINERνA detector are visually represented with a web-based too... more Neutrino interaction events in the MINERνA detector are visually represented with a web-based tool called Arachne. Data are retrieved from a central server via AJAX, and client-side JavaScript draws images into the user's browser window using the draft HTML 5 standard. These technologies allow neutrino interactions to be viewed by anyone with a web browser, allowing for easy hand-scanning of particle interactions. Arachne has been used in MINERνA to evaluate neutrino data in a prototype detector, to tune reconstruction algorithms, and for public outreach and education.

Use of a Scintillator Detector for Luminosity Measurements

High Energy Physics - Proceedings of the Fifth Latin American Symposium, 2006

One of the main goals of the V0 setup for the ALICE experiment at CERN will be the measurement of... more One of the main goals of the V0 setup for the ALICE experiment at CERN will be the measurement of the instantaneous luminosity passing by the ALICE detector. We study here this possibility and also the efficiency of this setup for different processes of inelastic production. The utility of this setup to reject events not coming for the interaction vertex and to reconstruct this vertex position is discused.

Physics Letters B, 2011

Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at 2.76 Te... more Inclusive transverse momentum spectra of primary charged particles in Pb-Pb collisions at 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross section. The measured charged particle spectra in |η| < 0.8 and 0.3 < p T < 20 GeV/c are compared to the expectation in pp collisions at the same √ s NN , scaled by the number of underlying nucleon-nucleon collisions. The comparison is expressed in terms of the nuclear modification factor R AA . The result indicates only weak medium effects (R AA ≈ 0.7) in peripheral collisions. In central collisions, R AA reaches a minimum of about 0.14 at p T = 6-7 GeV/c and increases significantly at larger p T . The measured suppression of high-p T particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb-Pb collisions at the LHC.

Physics Letters B, 2013

The elliptic, v 2 , triangular, v 3 , and quadrangular, v 4 , azimuthal anisotropic flow coeffici... more The elliptic, v 2 , triangular, v 3 , and quadrangular, v 4 , azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions and (anti-)protons in Pb-Pb collisions at √ s NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range |η| < 0.8 at different collision centralities and as a function of transverse momentum, p T , out to p T = 20 GeV/c. The observed non-zero elliptic and triangular flow depends only weakly on transverse momentum for p T > 8 GeV/c. The small p T dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to p T = 8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least p T = 8 GeV/c indicating that the particle type dependence persists out to high p T .

Physics Letters B, 2013

Angular correlations between charged trigger and associated particles are measured by the ALICE d... more Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < p T,assoc < p T,trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in highmultiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p T bins, and the widths show no significant evolution with event multiplicity or p T . These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge.

Journal of High Energy Physics, 2012

The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ ... more The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at $ \sqrt{s}=7 $ TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5.6 nb−1. The fraction of J/ψ from the decay of long-lived beauty hadrons was determined for J/ψ candidates with transverse momentum p t > 1.3 GeV/c and rapidity |y| < 0.9. The cross section for prompt J/ψ mesons, i.e. directly produced J/ψ and prompt decays of heavier charmonium states such as the ψ(2S) and χc resonances, is σprompt J/ψ (p t > 1.3 GeV/c, |y| < 0.9) = 8.3 ± 0.8 (stat.) ± 1.1 (syst.) $ _{-1.4}^{+1.5 } $ (syst. pol.) μb. The cross section for the production of b-hadrons decaying to J/ψ with p t > 1.3 GeV/c and |y| < 0.9 is $ {\sigma_{{{J \left/ {{\psi \leftarrow {{\mathrm{h}}_{\mathrm{B}}}}} \right.}}}} $ (p t > 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.) $ _{-0.32}^{+0.26 } $ (syst.) μb. The results are compared to QCD model predictio...

Journal of High Energy Physics, 2012

We present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ a... more We present measurements of Underlying Event observables in pp collisions at $ \sqrt {s} = 0.9 $ and 7TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p T,LT in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p T thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2–3 between the lower and higher collision energies, depending on the track p T threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed p T in the Tran...

Physics Letters B, 2012

The ALICE experiment has measured low-mass dimuon production in pp collisions at √ s = 7 TeV in t... more The ALICE experiment has measured low-mass dimuon production in pp collisions at √ s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (η, ρ, ω, η , φ) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for ω and φ are σ ω (1 < p t < 5 GeV/c, 2.5 < y < 4) = 5.28 ± 0.54(stat) ± 0.49(syst) mb and σ φ (1 < p t < 5 GeV/c, 2.5 < y < 4) = 0.940 ± 0.084(stat) ± 0.076(syst) mb. The differential cross sections d 2 σ /dy dp t are extracted as a function of p t for ω and φ. The ratio between the ρ and ω cross section is obtained. Results for the φ are compared with other measurements at the same energy and with predictions by models.

Physics Letters B, 2012

The ALICE Collaboration has measured inclusive J/ψ production in pp collisions at a center of mas... more The ALICE Collaboration has measured inclusive J/ψ production in pp collisions at a center of mass energy √ s = 2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y| < 0.9 and 2.5 < y < 4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L e int = 1.1 nb -1 and L µ int = 19.9 nb -1 , and the corresponding signal statistics are N e + e - J/ψ = 59 ± 11 and N = 1364 ± 53. We present dσ J/ψ /dy for the two rapidity regions under study and, for the forward-y range, d 2 σ J/ψ /dydp t in the transverse momentum domain 0 < p t < 8 GeV/c. The results are compared with previously published results at √ s = 7 TeV and with theoretical calculations. Inclusive J/ψ production in pp collisions at √ s = 2.76 TeV 3

Physics Letters B, 2012

Angular correlations between unidentified charged trigger (t) and associated (a) particles are me... more Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb-Pb collisions at s NN = 2.76 TeV for transverse momenta 0.25 < p t,a T < 15 GeV/c, where p t T > p a T . The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η| < 1.0. Distributions in relative azimuth φ ≡ φ tφ a are analyzed for | η| ≡ |η tη a | > 0.8, and are referred to as "long-range correlations". Fourier components V n ≡ cos(n φ) are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy V n (p t T , p a T ) is fully described in terms of single-particle anisotropies ). This expectation is tested for 1 n 5 by applying a global fit of all V n (p t T , p a T ) to obtain the best values v n {GF}(p T ). It is found that for 2 n 5, the fit agrees well with data up to p a T ∼ 3-4 GeV/c, with a trend of increasing deviation as p t T and p a T are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25 < p T < 15 GeV/c range using a single v n (p T ) curve; such a description is however approximately possible for 2 n 5 when p a T < 4 GeV/c. For the n = 1 harmonic, however, a single v 1 (p T ) curve is not obtained even within the reduced range p a T < 4 GeV/c.

Physics Letters B, 2010

We h a v e analysed a sample of 2.36 million minimum bias events produced in pp collisions at p s... more We h a v e analysed a sample of 2.36 million minimum bias events produced in pp collisions at p s = 630 GeV in the UA1 experiment at the CERN collider. We h a v e studied production of charged particles with transverse momenta (p T) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of hp T i with charged particle multiplicity m a y be related to changing production of low p T particles.