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Rossetti, Valerio
Publications (10 of 355) Show all publications
Abulaiti, Y., Åkerstedt, H., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., . . . Wallängen, V. (2018). Measurement of jet fragmentation in 5.02 TeV proton-lead and proton-proton collisions with the ATLAS detector. Nuclear Physics A, 978, 65-106
Open this publication in new window or tab >>Measurement of jet fragmentation in 5.02 TeV proton-lead and proton-proton collisions with the ATLAS detector
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2018 (English)In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 978, p. 65-106Article in journal (Refereed) Published
Abstract [en]

A measurement of the fragmentation functions of jets into charged particles in p Pb collisions and pp collisions is presented. The analysis utilizes 28 nb(-1) of p Pb data and 26 pb(-1) of pp data, both at root(TN)-T-s= 5.02 TeV, collected in 2013 and 2015, respectively, with the ATLAS detector at the LHC. The measurement is reported in the centre-of-mass frame of the nucleon-nucleon system for jets in the rapidity range vertical bar y*vertical bar <1.6 and with transverse momentum 45 < p(T) < 260 GeV. Results are presented both as a function of the charged-particle transverse momentum and as a function of the longitudinal momentum fraction of the particle with respect to the jet. The pp fragmentation functions are compared with results from Monte Carlo event generators and two theoretical models. The ratios of the p +Pb to pp fragmentation functions are found to be consistent with unity.

Keywords
Relativistic heavy-ion collisions, Jets, Fragmentation into hadrons
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161963 (URN)10.1016/j.nuclphysa.2018.07.006 (DOI)000446948800005 ()
Available from: 2018-11-12 Created: 2018-11-12 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2018). Measurement of the cross-section for producing a W boson in association with a single top quark in pp collisions at root s=13 TeV with ATLS. Journal of High Energy Physics (JHEP) (1), Article ID 063.
Open this publication in new window or tab >>Measurement of the cross-section for producing a W boson in association with a single top quark in pp collisions at root s=13 TeV with ATLS
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2018 (English)In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 1, article id 063Article in journal (Refereed) Published
Abstract [en]

The inclusive cross-section for the associated production of a W boson and top quark is measured using data from proton-proton collisions at root s = 13TeV. The dataset corresponds to an integrated luminosity of 3.2 fb(-1), and was collected in 2015 by the ATLAS detector at the Large Hadron Collider at CERN. Events are selected requiring two opposite sign isolated leptons and at least one jet; they are separated into signal and control regions based on their jet multiplicity and the number of jets that are identified as containing b hadrons. The Wt signal is then separated from the t ($) over bar background using boosted decision tree discriminants in two regions. The cross-section is extracted by fitting templates to the data distributions, and is measured to be sigma(Wt) = 94 +/- 10 (stat:)(-22)(+28) (syst:) +/- 2 (lumi:) pb. The measured value is in good agreement with the SM prediction of sigma(theory) = 71: 7 +/- 1: 8 (scale) +/- 3: 4 (PDF) pb [1].

Keywords
Hadron-Hadron scattering (experiments)
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-152627 (URN)10.1007/JHEP01(2018)063 (DOI)000423212200001 ()
Available from: 2018-02-06 Created: 2018-02-06 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., . . . Wallängen, V. (2018). Measurement of the W-boson mass in pp collisions at root s=7 TeV with the ATLAS detector. European Physical Journal C, 78(2), Article ID 110.
Open this publication in new window or tab >>Measurement of the W-boson mass in pp collisions at root s=7 TeV with the ATLAS detector
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2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 2, article id 110Article in journal (Refereed) Published
Abstract [en]

A measurement of the mass of the W boson is presented based on proton-proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb(-1) of integrated luminosity. The selected data sample consists of 7.8 x 10(6) candidates in the W -> mu nu channel and 5.9 x 10(6) candidates in the W -> e nu channel. The W-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the W boson transverse mass in the electron and muon decay channels, yielding m(W) = 80370 +/- 7 (stat.) +/- 11(exp. syst.) +/- 14 (mod. syst.) MeV = 80370 +/- 19 MeV, where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the W+ and W- bosons yields m(W+) - m(W-) = -29 +/- 28 MeV.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-153777 (URN)10.1140/epjc/s10052-017-5475-4 (DOI)000424385500005 ()
Available from: 2018-03-20 Created: 2018-03-20 Last updated: 2022-03-23Bibliographically approved
Åkerstedt, H., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., Carney, R. M. D., Clement, C., . . . Wallängen, V. (2018). Operation and performance of the ATLAS Tile Calorimeter in Run 1. European Physical Journal C, 78(12), Article ID 987.
Open this publication in new window or tab >>Operation and performance of the ATLAS Tile Calorimeter in Run 1
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2018 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 12, article id 987Article in journal (Refereed) Published
Abstract [en]

The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter's performance during the years 2008-2012 using cosmic-ray muon events and proton-proton collision data at centre-of-mass energies of 7 and 8 TeV with a total integrated luminosity of nearly 30 fb(-1). The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton-proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-167704 (URN)10.1140/epjc/s10052-018-6374-z (DOI)000459286600002 ()30872953 (PubMedID)
Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2017). A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector. European Physical Journal C, 77(1), Article ID 26.
Open this publication in new window or tab >>A measurement of the calorimeter response to single hadrons and determination of the jet energy scale uncertainty using LHC Run-1 pp-collision data with the ATLAS detector
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

A measurement of the calorimeter response to isolated charged hadrons in the ATLAS detector at the LHC is presented. This measurement is performed with 3.2 nb(-1) of proton-proton collision data at root s = 7 TeV from 2010 and 0.1 nb(-1) of data at root s = 8 TeV from 2012. A number of aspects of the calorimeter response to isolated hadrons are explored. After accounting for energy deposited by neutral particles, there is a 5% discrepancy in the modelling, using various sets of GEANT4 hadronic physics models, of the calorimeter response to isolated charged hadrons in the central calorimeter region. The description of the response to anti-protons at low momenta is found to be improved with respect to previous analyses. The electromagnetic and hadronic calorimeters are also examined separately, and the detector simulation is found to describe the response in the hadronic calorimeter well. The jet energy scale uncertainty and correlations in scale between jets of different momenta and pseudorapidity are derived based on these studies. The uncertainty is 2-5% for jets with transverse momenta above 2 TeV, where this method provides the jet energy scale uncertainty for ATLAS.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-141393 (URN)10.1140/epjc/s10052-016-4580-0 (DOI)000392335600003 ()28260979 (PubMedID)
Available from: 2017-05-02 Created: 2017-05-02 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2017). Electron efficiency measurements with the ATLAS detector using 2012 LHC proton-proton collision data. European Physical Journal C, 77(3), Article ID 195.
Open this publication in new window or tab >>Electron efficiency measurements with the ATLAS detector using 2012 LHC proton-proton collision data
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, no 3, article id 195Article in journal (Refereed) Published
Abstract [en]

This paper describes the algorithms for the reconstruction and identification of electrons in the central region of the ATLAS detector at the Large Hadron Collider (LHC). These algorithms were used for all ATLAS results with electrons in the final state that are based on the 2012 pp collision data produced by the LHC at root s = 8 TeV. The efficiency of these algorithms, together with the charge misidentification rate, is measured in data and evaluated in simulated samples using electrons from Z -> ee, Z -> ee gamma and J/Psi -> ee decays. For these efficiency measurements, the full recorded data set, corresponding to an integrated luminosity of 20.3 fb(-1), is used. Based on a new reconstruction algorithm used in 2012, the electron reconstruction efficiency is 97% for electrons with E-T = 15 GeV and 99% at E-T = 50 GeV. Combining this with the efficiency of additional selection criteria to reject electrons from background processes or misidentified hadrons, the efficiency to reconstruct and identify electrons at the ATLAS experiment varies from 65 to 95%, depending on the transverse momentum of the electron and background rejection.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-144740 (URN)10.1140/epjc/s10052-017-4756-2 (DOI)000398956200005 ()28579919 (PubMedID)
Available from: 2017-06-27 Created: 2017-06-27 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., Bohm, C., . . . Wallängen, V. (2017). Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC. Nature Physics, 13(9), 852-858
Open this publication in new window or tab >>Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS detector at the LHC
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2017 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 13, no 9, p. 852-858Article in journal (Refereed) Published
Abstract [en]

Light-by-light scattering (gamma gamma -> gamma gamma) is a quantum-mechanical process that is forbidden in the classical theory of electrodynamics. This reaction is accessible at the Large Hadron Collider thanks to the large electromagnetic field strengths generated by ultra-relativistic colliding lead ions. Using 480 mu b(-1) of lead-lead collision data recorded at a centre-of-mass energy per nucleon pair of 5.02 TeV by the ATLAS detector, here we report evidence for light-by-light scattering. A total of 13 candidate events were observed with an expected background of 2.6 +/- 0.7 events. After background subtraction and analysis corrections, the fiducial cross-section of the process Pb + Pb (gamma gamma) -> Pb-(center dot) + Pb-(center dot) gamma gamma, for photon transverse energy E-T > 3 GeV, photon absolute pseudorapidity vertical bar eta vertical bar < 2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV and diphoton acoplanarity below 0.01, is measured to be 70 +/- 24 (stat.) +/- 17 (syst.) nb, which is in agreement with the standard model predictions.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-147887 (URN)10.1038/NPHYS4208 (DOI)000409235100017 ()
Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2017). Femtoscopy with identified charged pions in proton-lead collisions at root s(NN)=5.02 TeV with ATLAS. Physical Review C: Covering Nuclear Physics, 96(6), Article ID 064908.
Open this publication in new window or tab >>Femtoscopy with identified charged pions in proton-lead collisions at root s(NN)=5.02 TeV with ATLAS
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2017 (English)In: Physical Review C: Covering Nuclear Physics, ISSN 2469-9985, E-ISSN 2469-9993, Vol. 96, no 6, article id 064908Article in journal (Refereed) Published
Abstract [en]

Bose-Einstein correlations between identified charged pions are measured for p+Pb collisions at root s(NN) = 5.02 TeV using data recorded by the ATLAS detector at the CERN Large Hadron Collider corresponding to a total integrated luminosity of 28 nb(-1). Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum (k(T)) and rapidity (y*(pi pi)) of the pair. Pairs are selected with a rapidity -2 < y*(pi pi) < 1 and with an average transverse momentum 0.1 < k(T) < 0.8 GeV. The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair k(T). A correlation of the radii with the local charged-particle density is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a selection of initial-geometry models. The cross term R-ol is measured as a function of rapidity, and a nonzero value is observed with 5.1 sigma combined significance for -1 < y*pi pi < 1 in the most central events.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-152495 (URN)10.1103/PhysRevC.96.064908 (DOI)000418917300004 ()
Available from: 2018-02-07 Created: 2018-02-07 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2017). Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8TeV using data collected by the ATLAS detector. European Physical Journal C, 77(8), Article ID 531.
Open this publication in new window or tab >>Fiducial, total and differential cross-section measurements of t-channel single top-quark production in pp collisions at 8TeV using data collected by the ATLAS detector
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2017 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 77, no 8, article id 531Article in journal (Refereed) Published
Abstract [en]

Detailed measurements of t-channel single top-quark production are presented. They use 20.2 fb(-1) of data collected by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of 8 TeV at the LHC. Total, fiducial and differential cross-sections are measured for both top-quark and top-antiquark production. The fiducial cross-section is measured with a precision of 5.8% (top quark) and 7.8% (top antiquark), respectively. The total cross-sections are measured to be stot(tq) = 56.7(-3.8)(+4.3) pb for top-quark production and sigma(tot)((t) over barq) = 32.9(-2.7)(+3.0) pb for top-antiquark production, in agreement with the Standard Model prediction. In addition, the ratio of top-quark to top-antiquark production cross-sections is determined to be R-t = 1.72 +/- 0.09. The differential cross-sections as a function of the transverse momentum and rapidity of both the top quark and the top antiquark are measured at both the parton and particle levels. The transverse momentum and rapidity differential cross-sections of the accompanying jet from the t-channel scattering are measured at particle level. All measurements are compared to various Monte Carlo predictions as well as to fixed-order QCD calculations where available.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-147097 (URN)10.1140/epjc/s10052-017-5061-9 (DOI)000407502800003 ()
Available from: 2017-10-11 Created: 2017-10-11 Last updated: 2022-03-23Bibliographically approved
Abulaiti, Y., Åkerstedt, H., Åsman, B., Bendtz, K., Bertoli, G., Bessidskaia Bylund, O., . . . Wallängen, V. (2017). High-E-T isolated-photon plus jets production in pp collisions at root s=8 TeV with the ATLAS detector. Nuclear Physics B, 918, 257-316
Open this publication in new window or tab >>High-E-T isolated-photon plus jets production in pp collisions at root s=8 TeV with the ATLAS detector
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2017 (English)In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 918, p. 257-316Article in journal (Refereed) Published
Abstract [en]

The dynamics of isolated-photon plus one-, two- and three-jet production in pp collisions at a centre-of-mass energy of 8 TeV are studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 20.2 fb(-1). Measurements of isolated-photon plus jets cross sections are presented as functions of the photon and jet transverse momenta. The cross sections as functions of the azimuthal angle between the photon and the jets, the azimuthal angle between the jets, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system are presented. The pattern of QCD radiation around the photon and the leading jet is investigated by measuring jet production in an annular region centred on each object; enhancements are observed around the leading jet with respect to the photon in the directions towards the beams. The experimental measurements are compared to several different theoretical calculations, and overall a good description of the data is found.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-144480 (URN)10.1016/j.nuclphysb.2017.03.006 (DOI)000401097200012 ()
Available from: 2017-06-21 Created: 2017-06-21 Last updated: 2022-03-23Bibliographically approved
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