Alberto Gago - 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.

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%.

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.

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.

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, 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.

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%.

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.

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.

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, 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.