Papers by H. Castilla-valdez
Journal of Instrumentation, 2013
ABSTRACT
Journal of High Energy Physics, 2012
Shape, transverse size, and charged-hadron multiplicity of jets in pp collisions at √ s = 7 TeV
Journal of High Energy Physics, 2012
The CMS collaboration
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
Search for heavy long-lived charged particles in pp collisions at √ s = 7 TeV ✩ .CMS Collaboratio... more Search for heavy long-lived charged particles in pp collisions at √ s = 7 TeV ✩ .CMS Collaboration CERN, Switzerland a r t i c l e i n f o a b s t r a c t
Journal of Instrumentation, 2012
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
ABSTRACT
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 2012
Journal of High Energy Physics, 2013
Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limi... more Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limits on ZZγ and Zγγ triple gauge boson couplings The CMS Collaboration * Abstract A measurement of the Zγ → ννγ cross section in pp collisions at √ s = 7 TeV is presented, using data corresponding to an integrated luminosity of 5.0 fb −1 collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range |η| < 1.4 with transverse energy above 145 GeV. The Zγ → ννγ production cross section is measured to be 21.1 ± 4.2 (stat.) ± 4.3 (syst.) ± 0.5 (lum.) fb, which agrees with the standard model prediction of 21.9 ± 1.1 fb. The results are combined with the CMS measurement of Zγ production in the + − γ final state (where is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings: |h Z 3 | < 2.7 × 10 −3 , |h Z 4 | < 1.3 × 10 −5 for ZZγ and |h γ 3 | < 2.9 × 10 −3 , |h γ 4 | < 1.5 × 10 −5 for Zγγ couplings.
European Physical Journal C, 2014
Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the... more Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at √ s N N = 5.02 TeV. Charged pions, kaons, and protons in the transverse-momentum range p T ≈ 0.1-1.7 GeV/c and laboratory rapidity |y| < 1 are identified via their energy loss in the silicon tracker. The average p T increases with particle mass and the charged multiplicity of the event. The increase of the average p T with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The p T spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity. C. Caillol, B. Clerbaux, G.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions w... more A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions with 35 pb −1 of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable R, related to the missing transverse energy E miss T . The new physics signal is characterized by a broad peak in the distribution of M R , an event-by-event indicator of the heavy particle mass scale. This new approach is complementary to E miss T -based searches. After background modeling based on data, and background rejection based on R and M R , no significant excess of events is found beyond the standard model expectations. The results are interpreted in the context of the constrained minimal supersymmetric standard model as well as two simplified supersymmetry models.
Journal of High Energy Physics, 2011
A measurement of the lepton charge asymmetry in inclusive pp → WX production at √ s = 7 TeV is pr... more A measurement of the lepton charge asymmetry in inclusive pp → WX production at √ s = 7 TeV is presented based on data recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 36 pb −1 . This high precision measurement of the lepton charge asymmetry, performed in both the W → eν and W → µν channels, provides new insights into parton distribution functions.
Physics Letters B, 2013
Results from the first study of isolated-photon + jet correlations in relativistic heavy ion coll... more Results from the first study of isolated-photon + jet correlations in relativistic heavy ion collisions are reported. The analysis uses data from PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair corresponding to an integrated luminosity of 150 μb −1 recorded by the CMS experiment at the LHC. For events containing an isolated photon with transverse momentum p γ T > 60 GeV/c and an associated jet with p Jet T > 30 GeV/c, the photon + jet p T imbalance is studied as a function of collision centrality and compared to pp data and pythia calculations at the same collision energy. Using the p γ T of the isolated photon as an estimate of the momentum of the associated parton at production, this measurement allows an unbiased characterisation of the in-medium parton energy loss. For more central PbPb collisions, a significant decrease in the ratio p
Physical Review D, 2014
ABSTRACT Measurements of the differential cross sections for the production of exactly four jets ... more ABSTRACT Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum p[subscript T] and pseudorapidity η, together with the correlations in azimuthal angle and the p[subscript T] balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb[superscript −1]. The cross section for exactly four jets, with two hard jets of p[subscript T] &gt; 50 GeV each, together with two jets of p[subscript T] &gt; 20 GeV each, within |η| &lt; 4.7 is measured to be σ = 330 ± 5(stat.) ± 45(syst.) nb. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data.
Physical Review D, 2014
ABSTRACT
Physical Review D, 2013
ABSTRACT
Journal of High Energy Physics, 2014
ABSTRACT
Physical review letters, Jan 13, 2014
We report the first observation of single-top-quark production in the s channel through the combi... more We report the first observation of single-top-quark production in the s channel through the combination of the CDF and D0 measurements of the cross section in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb(-1) per experiment. The measured cross section is σ(s) = 1.29(-0.24)(+0.26) pb. The probability of observing a statistical fluctuation of the background to a cross section of the observed size or larger is 1.8 × 10(-10), corresponding to a significance of 6.3 standard deviations for the presence of an s-channel contribution to the production of single-top quarks.
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Papers by H. Castilla-valdez