Publications (994)3002.94 Total impact
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ABSTRACT: A search for a new resonance decaying to a W or Z boson and a Higgs boson in the [Formula: see text] final states is performed using 20.3 fb[Formula: see text] of pp collision data recorded at [Formula: see text] 8 TeV with the ATLAS detector at the Large Hadron Collider. The search is conducted by examining the WH / ZH invariant mass distribution for a localized excess. No significant deviation from the Standard Model background prediction is observed. The results are interpreted in terms of constraints on the Minimal Walking Technicolor model and on a simplified approach based on a phenomenological Lagrangian of Heavy Vector Triplets.European Physical Journal C 06/2015; 75(6):263. DOI:10.1140/epjc/s100520153474x · 5.08 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Various differential crosssections are measured in topquark pair \( \left(t\overline{t}\right) \) events produced in protonproton collisions at a centreofmass energy of \( \sqrt{s}=7 \) TeV at the LHC with the ATLAS detector. These differential crosssections are presented in a data set corresponding to an integrated luminosity of 4.6 fb−1. The differential crosssections are presented in terms of kinematic variables, such as momentum, rapidity and invariant mass, of a topquark proxy referred to as the pseudotopquark as well as the pseudotopquark pair system. The dependence of the measurement on theoretical models is minimal. The measurements are performed on \( t\overline{t} \) events in the lepton+jets channel, requiring exactly one charged lepton and at least four jets with at least two of them tagged as originating from a bquark. The hadronic and leptonic pseudotopquarks are defined via the leptonic or hadronic decay mode of the W boson produced by the topquark decay in events with a single charged lepton. Differential crosssection measurements of the pseudotopquark variables are compared with several Monte Carlo models that implement nexttoleading order or leadingorder multileg matrixelement calculations.Journal of High Energy Physics 06/2015; 2015(6). DOI:10.1007/JHEP06(2015)100 · 6.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H→γγ and H→ZZ→4ℓ decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is m_H=125.09±0.21 (stat)±0.11 (syst) GeV.Physical Review Letters 05/2015; 114(19):191803. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report a measurement of the timedependent CP asymmetry of B0>D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetricenergy B factories PEPII at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/ 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/ 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters eta_f S = +0.66 +/ 0.10 (stat.) +/ 0.06 (syst.) and C = 0.02 +/ 0.07 (stat.) +/ 0.03 (syst.). These results correspond to the first observation of CP violation in B0>D(*)CP h0 decays. The hypothesis of no mixinginduced CP violation is excluded in these decays at the level of 5.4 standard deviations.  [Show abstract] [Hide abstract]
ABSTRACT: We present a search for a neutral, longlived particle L that is produced in e^{+}e^{} collisions and decays at a significant distance from the e^{+}e^{} interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e^{+}e^{} data sample with a luminosity of 489.1 fb^{1} collected by the BABAR detector at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and just below the ϒ(4S). Fitting the twotrack mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible twobody L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B→X_{s}L), where X_{s} is a strange hadronic system.Physical Review Letters 05/2015; 114(17):171801. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a search for a neutral, longlived particle L that is produced in e[superscript +]e[superscript ] collisions and decays at a significant distance from the e[superscript +]e[superscript ] interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e[superscript +]e[superscript ] data sample with a luminosity of 489.1 fb[superscript 1] collected by the BABAR detector at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and just below the ϒ(4S). Fitting the twotrack mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible twobody L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B → X[subscript s]L), where X[subscript s] is a strange hadronic system.  [Show abstract] [Hide abstract]
ABSTRACT: A search is presented for the decay ϒ(1S)→γA[superscript 0], A[superscript 0] → c[bar over c], where A[superscript 0] is a candidate for the CPodd Higgs boson of the nexttominimal supersymmetric standard model. The search is based on data collected with the BABAR detector at the ϒ(2S) resonance. A sample of ϒ(1S) mesons is selected via the decay ϒ(2S) → π[superscript +]π[superscript ]ϒ(1S). The A[superscript 0] → c[bar over c] decay is identified through the reconstruction of hadronic D[superscript 0], D[superscript +], and D[superscript *](2010)[superscript +] meson decays. No significant signal is observed. The measured 90% confidencelevel upper limits on the product branching fraction B(ϒ(1S) → γA[superscript 0]) × B(A[superscript 0] → c[bar over c]) range from 7.4 × 10[superscript 5] to 2.4 × 10[superscript 3] for A[superscript 0] masses from 4.00 to 8.95 GeV/c[superscript 2] and 9.10 to 9.25 GeV/c[superscript 2], where the region between 8.95 and 9.10 GeV/c[superscript 2] is excluded because of background from ϒ(2S) → γχ[subscript bJ](1P), χ[subscript bJ](1P) → γϒ(1S) decays.  [Show abstract] [Hide abstract]
ABSTRACT: We perform a measurement of the τ → lγν[bar over ν] (l = e,μ) branching fractions for a minimum photon energy of 10 MeV in the τ rest frame, using 431 fb[superscript 1] of e[superscript +]e[superscript ] collisions collected at the centerofmass energy of the ϒ(4S) resonance with the BABAR detector at the PEPII storage rings. We find B(τ → μγν[bar over ν]) = (3.69 ± 0.03 ± 0.10) × 10[superscript 3] and B(τ → eγν[bar over ν]) = (1.847 ± 0.015 ± 0.052) × 10[superscript 2], where the first quoted error is statistical and the second is systematic. These results are substantially more precise than previous measurements.  [Show abstract] [Hide abstract]
ABSTRACT: Based on a sample of 500 million e[superscript +]e[superscript ] → c[bar over c] events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay D[superscript 0] → π[superscript ]e[superscript +]ν[subscript e]. We measure the ratio of branching fractions, R[subscript D] = B(D[superscript 0] → π[superscript ]e[superscript +]ν[subscript e])/B(D[superscript 0] → K[superscript ]π[superscript +]) = 0.0713 ± 0.0017[subscript stat] ± 0.0024[subscript syst], and use the present world average for B(D[superscript 0] → K[superscript ]π[superscript +] to obtain B(D[superscript 0] → π[superscript ]e[superscript +]ν[subscript e]) = (2.770 ± 0.068[subscript stat] ± 0.092[subscript syst] ± 0.037[subscript ext]) × 10[superscript 3] where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on q[superscript 2], the fourmomentum transfer squared between the D and the π meson, is compared to various theoretical predictions for the hadronic form factor, f[π over +,D](q[superscript 2]), and the normalization V[subscript cd] × f[π over +,D](q[superscript 2] = 0) = 0.1374 ± 0.0038[subscript stat] ± 0.0022[subscript syst] ± 0.0009[subscript ext] is extracted from a fit to data. Using the most recent LQCD prediction of f[π over +,D](q[superscript 2] = 0) = 0.666 ± 0.029, we obtain V[subscript cd] = 0.206 ± 0.007[subscript exp] ± 0.009[subscript LQCD]. Assuming, instead, V[subscript cd] = V[subscript us] = 0.2252 ± 0.0009, we obtain f[π over +,D](q[superscript 2] = 0) = 0.610 ± 0.020subscript exp] ± 0.005[subscript ext]. The q[superscript 2] dependence of f[π over +,D](q[superscript 2]) is compared to a variety of multipole parametrizations. This information is applied to B[superscript 0] → π[superscript ]e[superscript +]ν[subscript e] decays and, combined with an earlier B[superscript 0] → π[superscript ]e[superscript +]ν[subscript e] measurement by BABAR, is used to derive estimates of V[subscript ub].  [Show abstract] [Hide abstract]
ABSTRACT: The results of a search for charged Higgs bosons decaying to a tau lepton and a neutrino, H+/ > tau(+/) nu, are presented. The analysis is based on 19.5 fb(1) of protonproton collision data at root s = 8TeV collected by the ATLAS experiment at the Large Hadron Collider. Charged Higgs bosons are searched for in events consistent with topquark pair production or in associated production with a top quark, depending on the considered H+/ mass. The final state is characterised by the presence of a hadronic tau decay, missing transverse momentum, btagged jets, a hadronically decaying W boson, and the absence of any isolated electrons or muons with high transverse momenta. The data are consistent with the expected background from Standard Model processes. A statistical analysis leads to 95% confidencelevel upper limits on the product of branching ratios B (t > bH(+/)) x B (H+/ > tau(+/) nu), between 0.23% and 1.3% for charged Higgs boson masses in the range 80160GeV. It also leads to 95% confidencelevel upper limits on the production cross section times branching ratio, sigma(pp > tH(+/)+ X) x B (H+/ > tau(+/)nu), between 0.76 pb and 4.5 fb, for charged Higgs boson masses ranging from 180 GeV to 1000 GeV. In the context of different scenarios of the Minimal Supersymmetric Standard Model, these results exclude nearly all values of tan beta above one for charged Higgs boson masses between 80 GeV and 160 GeV, and exclude a region of parameter space with high tan beta for H+/ masses between 200 GeV and 250 GeV.Journal of High Energy Physics 03/2015; · 6.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present Dalitz plot analyses for the decays of B mesons to D[superscript −]D[superscript 0]K[superscript +] and [bar over D][superscript 0]D[superscript 0]K[superscript +]. We report the observation of the D[* over s1](2700)[superscript +] resonance in these two channels and obtain measurements of the mass M(D[* over s1](2700)[superscript +]) = 2699[+14 over −7] MeV/c[superscript 2] and of the width Γ(D[* over s1](2700)[superscript +]) = 127[+24 over −19] MeV, including statistical and systematic uncertainties. In addition, we observe an enhancement in the D[superscript 0]K[superscript +] invariant mass around 2350–2500 MeV/c[superscript 2] in both decays B[superscript 0] → D[superscript −]D[superscript 0]K[superscript +] and B[superscript +] → [bar over D][superscript 0]D[superscript 0]K[superscript +], which we are not able to interpret. The results are based on 429 fb[superscript −1] of data containing 471×10[superscript 6]B[bar over B] pairs collected at the ϒ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory.  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the asymmetry A_{CP} between samesign inclusive dilepton samples ℓ^{+}ℓ^{+} and ℓ^{}ℓ^{} (ℓ=e, μ) from semileptonic B decays in ϒ(4S)→BB[over ¯] events, using the complete data set recorded by the BABAR experiment near the ϒ(4S) resonance, corresponding to 471×10^{6} BB[over ¯] pairs. The asymmetry A_{CP} allows comparison between the mixing probabilities P(B[over ¯]^{0}→B^{0}) and P(B^{0}→B[over ¯]^{0}), and therefore probes CP and T violation. The result, A_{CP}=[3.9±3.5(stat)±1.9(syst)]×10^{3}, is consistent with the standard model expectation.Physical Review Letters 02/2015; 114(8):081801. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Searches are performed for resonant and nonresonant Higgs boson pair production in the γγbb[over ¯] final state using 20 fb^{1} of protonproton collisions at a centerofmass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the backgroundonly hypothesis. The limit observed in the search for a narrow X→hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.Physical Review Letters 02/2015; 114(8):081802. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We report the observation of the baryonic decay [bar over B][superscript 0 → Λ[+ over c][bar over p]K[superscript ]K[superscript +] using a data sample of 471 × 10[superscript 6] B[bar over B] pairs produced in e[superscript +]e[superscript ] annihilations at √s = 10.58 GeV. This data sample was recorded with the BABAR detector at the PEPII storage ring at SLAC. We find B([bar over B][superscript 0 → Λ[+ over c][bar over p]K[superscript ]K[superscript +]) = (2.5 ± 0.4[subscript (stat)] ± 0.2[subscript (syst)] ± 0.6[subscript B(Λ[+ over c])) × 10[superscript 5], where the uncertainties are statistical, systematic, and due to the uncertainty of the Λ[+ over c] → pK[superscript ]π[superscript +] branching fraction, respectively. The result has a significance corresponding to 5.0 standard deviations, including all uncertainties. For the resonant decay [bar over B][superscript 0] → Λ[+ over c][bar over p]ϕ, we determine the upper limit B([bar over B][superscript 0] → Λ[+ over c][bar over p]ϕ) < 1.2 × 10[superscript 5] at 90% confidence level.  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the asymmetry A[subscript CP] between samesign inclusive dilepton samples ℓ[superscript +]ℓ[superscript +] and ℓ[superscript −]ℓ[superscript −] (ℓ=e, μ) from semileptonic B decays in Υ(4S)→B[bar over B] events, using the complete data set recorded by the BABAR experiment near the Υ(4S) resonance, corresponding to 471×10[superscript 6] B[bar over B] pairs. The asymmetry A[subscript CP] allows comparison between the mixing probabilities P([bar over B][superscript 0]→B[superscript 0]) and P(B[superscript 0]→[bar over B][superscript 0]), and therefore probes CP and T violation. The result, A[subscript CP]=[−3.9±3.5(stat)±1.9(syst)]×10[superscript −3], is consistent with the standard model expectation.  [Show abstract] [Hide abstract]
ABSTRACT: Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at sqrt[s_{NN}]=2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb^{1}, respectively. The jets are identified with the antik_{t} algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32<p_{T}<500 GeV and absolute rapidity y<2.1 and as a function of collision centrality. The nuclear modification factor R_{AA} is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The R_{AA} shows a slight increase with p_{T} and no significant variation with rapidity.Physical Review Letters 02/2015; 114(7):072302. · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study the rare B meson decays B[superscript ±,0] → [J over ψ K [superscript +] K [superscript −] K [superscript ±,0]], B[superscript ±,0] → [J over ψϕK[superscript ±,0]], and search for B[superscript 0] → [J over ψϕ], using 469 × 10[superscript 6] B[bar over B] events collected at the ϒ(4S) resonance with the BABAR detector at the PEPII e[superscript +]e[superscript ] asymmetric energy collider. We present new measurements of branching fractions and a study of the [J over ψϕ] mass distribution in search of new charmoniumlike states. In addition, we search for the decay B[superscript 0] → [J over ψϕ] and find no evidence of a signal.  [Show abstract] [Hide abstract]
ABSTRACT: We use (121 ± 1) million Υ(3S) and (98 ± 1) million Υ(2S) mesons recorded by the BABAR detector at the PEPII e[superscript +]e[superscript ] collider at SLAC to perform a study of radiative transitions involving the χ[subscript bJ](1P,2P) states in exclusive decays with μ[superscript +]μ[superscript ]γγ final states. We reconstruct twelve channels in four cascades using two complementary methods. In the first we identify both signal photon candidates in the electromagnetic calorimeter (EMC), employ a calorimeter timingbased technique to reduce backgrounds, and determine branchingratio products and fine mass splittings. These results include the best observational significance yet for the χ[subscript b0](2P) → γΥ(2S) and χ[subscript b0](1P) → γΥ(1S) transitions. In the second method, we identify one photon candidate in the EMC and one which has converted into an e[superscript +]e[superscript ] pair due to interaction with detector material, and we measure absolute product branching fractions. This method is particularly useful for measuring Υ(3S) → γχ[subscript b1,2](1P) decays. Additionally, we provide the most uptodate derived branching fractions, matrix elements and mass splittings for χ[subscript b] transitions in the bottomonium system. Using a new technique, we also measure the two lowestorder spindependent coefficients in the nonrelativistic QCD Hamiltonian. 
Article: Search for new π[superscript 0]like particles produced in association with a τlepton pair
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ABSTRACT: We report on a search in e[superscript +]e[superscript ] annihilations for new π[superscript 0]like particles produced in association with a τlepton pair. These objects, with a similar mass and similar decay modes to π[superscript 0] mesons, could provide an explanation for the nonasymptotic behavior of the pionphoton transition form factor observed by the BABAR Collaboration. No significant signal is observed, and limits on the production cross section at the level of 73 fb or 370 fb, depending on the model parameters, are determined at 90% confidence level. These upper limits lie below the cross section values needed to explain the BABAR form factor data.  Physical Review D 01/2015; 91(1). DOI:10.1103/PhysRevD.91.019901 · 4.64 Impact Factor
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Institutions

2015

University of Granada
Granata, Andalusia, Spain


2005–2015

RuhrUniversität Bochum
 Institut für Experimentalphysik I
Bochum, North RhineWestphalia, Germany


2012–2013

University of Freiburg
 Faculty of Mathematics and Physics
Freiburg, Lower Saxony, Germany 
University of British Columbia  Vancouver
Vancouver, British Columbia, Canada


2006–2009

Université de Savoie
Chambéry, RhôneAlpes, France


2008

University of Rostock
Rostock, MecklenburgVorpommern, Germany
