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Helsingin yliopiston tutkijoiden julkaisemia artikkeleja.

Helsingin yliopiston tutkijat voivat rinnakkaistallentaa tutkimusjulkaisujansa HELDAan liittämällä kokotekstin julkaisuun TUHAT-tutkimustietojärjestelmässä. (Toimintaohje tutkijalle)

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Uusimmat julkaisut

  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    The CMS muon detector system, muon reconstruction software, and high-level trigger underwent significant changes in 2013-2014 in preparation for running at higher LHC collision energy and instantaneous luminosity. The performance of the modified system is studied using proton-proton collision data at center-of-mass energy root s = 13 TeV, collected at the LHC in 2015 and 2016. The measured performance parameters, including spatial resolution, efficiency, and timing, are found to meet all design specifications and are well reproduced by simulation. Despite the more challenging running conditions, the modified muon system is found to perform as well as, and in many aspects better than, previously. We dedicate this paper to the memory of Prof. Alberto Benvenuti, whose work was fundamental for the CMS muon detector.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    The results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the M-T2 variable. The analysis uses proton-proton collision data at root s = 13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb(-1). Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to t nu, and 50% to b tau, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to t nu, LQ masses below 1530 GeV are excluded assuming the Yang-Mills case with coupling kappa = 1, or 1115 GeV in the minimal coupling case kappa = 0, placing the most stringent constraint to date from pair production of vector LQs.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    The pseudorapidity distributions of dijets as functions of their average transverse momentum (p(T)(ave)) are measured in proton-lead (pPb) and proton-proton (pp) collisions. The data samples were collected by the CMS experiment at the CERN LHC, at a nucleon-nucleon center-of-mass energy of 5.02 TeV. A significant modification of the pPb spectra with respect to the pp spectra is observed in all p(T)(ave) intervals investigated. The ratios of the pPb and pp distributions are compared to next-to-leading order perturbative quantum chromodynamics calculations with unbound nucleon and nuclear parton distribution functions (PDFs). These results give the first evidence that the gluon PDF at large Bjorken x in lead ions is strongly suppressed with respect to the PDF in unbound nucleons.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    The elliptic azimuthal anisotropy coefficient (upsilon(2)) is measured for charm (D-0) and strange (K-S(0), Lambda, Xi(-), and Omega(-)) hadrons, using a data sample of p + Pb collisions collected by the CMS experiment, at a nucleonnucleon center-of- mass energy of root(NN)-N-s = 8.16 TeV. A significant positive upsilon(2) signal from long- range azimuthal correlations is observed for all particle species in high- multiplicity p + Pb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller upsilon(2) than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at root(NN)-N-s = 5.02 TeV, also presented.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    Results are reported from a search for physics beyond the standard model in proton-proton collisions at a center-of-mass energy of root s=13TeV. The search uses a signature of a single lepton, large jet and bottom quark jet multiplicities, and high sum of large-radius jet masses, without any requirement on the missing transverse momentum in an event. The data sample corresponds to an integrated luminosity of 35.9 fb(-1) recorded by the CMS experiment at the LHC. No significant excess beyond the prediction from standard model processes is observed. The results are interpreted in terms of upper limits on the production cross section for R-parity violating supersymmetric extensions of the standard model using a benchmark model of gluino pair production, in which each gluino decays promptly via (g) over tilde -> tbs. Gluinos with a mass below 1610 GeV are excluded at 95% confidence level. (c) 2018 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    Pseudorapidity, transverse momentum, and multiplicity distributions are measured in the pseudorapidity range vertical bar eta vertical bar < 2.4 for charged particles with transverse momenta satisfying pT > 0.5 GeV in proton-proton collisions at a center-of-mass energy of root s = 13 TeV. Measurements are presented in three different event categories. The most inclusive of the categories corresponds to an inelastic pp data set, while the other two categories are exclusive subsets of the inelastic sample that are either enhanced or depleted in single diffractive dissociation events. The measurements are compared to predictions from Monte Carlo event generators used to describe high-energy hadronic interactions in collider and cosmic-ray physics.
  • The CMS collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T. (2018)
    A measurement is presented of the effective leptonic weak mixing angle (sin(2) theta(effl))using the forward- backward asymmetry of Drell-Yan lepton pairs (mu mu and ee) produced in proton-proton collisions at N root s = 8 TeV at the CMS experiment of the LHC. The data correspond to integrated luminosities of 18.8 and 19.6 fb(-1) in the dimuon and dielectron channels, respectively, containing 8.2 million dimuon and 4.9 million dielectron events. With more events and new analysis techniques, including constraints obtained on the parton distribution functions from the measured forward-backward asymmetry, the statistical and systematic uncertainties are significantly reduced relative to previous CMS measurements. The extracted value of sin(2) theta(effl) from the combined dilepton data is sin(2) theta(effl) = 0.23101 +/- 0.00036 (stat) +/- 0.00018 (syst) 0.00016 (theo) +/- 0.00031 (parton distributions in proton) = 0.23101 +/- 0.00053.
  • The CMS collaboration; TOTEM Collaboration; Sirunyan, A. M.; Eerola, P.; Kirschenmann, H.; Pekkanen, J.; Voutilainen, M.; Havukainen, J.; Heikkilä, J. K.; Järvinen, T.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Laurila, S.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Siikonen, H.; Tuominen, E.; Tuominiemi, J.; Tuuva, T.; Berretti, M.; Garcia, F.; Heino, J.; Lauhakangas, R.; Naaranoja, T.; Oljemark, F.; Österberg, K.; Saarikko, H.; Welti, J. (2018)
    The process pp -> pl(+)l(-)p(()*()), with l(+)l(-) a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at root s = 13 TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p*, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb(-1) collected during standard, high-luminosity LHC operation. A total of 12 mu(+)/mu(-) and 8 e(+)e(-) pairs with m(l(+)l(-)) > 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 +/- 0.07 (stat) +/- 0.53 (syst) and 2.36 +/- 0.09 (stat) +/- 0.47(syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged gamma gamma collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.
  • Kärnä-Behm, Jaana (2016)
    Probing is a new, playful co-design method that enables future users to participate in a design process in variant design contexts. This article is based on a case study of applying and developing the probing method as a part of studies of interior design in higher education in craft and design. The article reports probing processes of the university-level students (N=72), training to become textile teachers, and their reflections on the method. The data on the case were collected during two interior design courses held in a single institution in 2014 and 2015. The results outline the students’ processes from the point of view of participation, spaces chosen as well as their reflections. After the students experienced the probing process, they suggested ideas for its application in teaching design in different educational degrees as well as applications in other contexts.
  • CDF Collaboration; D0 Collaboration; Aaltonen, T.; Abazov, V. M.; Brücken, E.; Devoto, F.; Mehtälä, P.; Orava, R. (2018)
    Drell-Yan lepton pairs produced in the process p (p) over bar -> l(+)l(-) + X through an intermediate gamma*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin(2) theta(lept)(eff) using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb(-1) of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin(2)theta(lept)(eff) = 0.23148 +/- 0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin(2) theta(W), or equivalently the W-boson mass M-W, using the ZFITTER software package yields sin(2) theta(W) = 0.22324 +/- 0.00033 or equivalently, M-W = 80.367 +/- 0.017 GeV/c(2).
  • The ALICE collaboration; Acharya, S.; Brucken, E. J.; Chang, B.; Hilden, T. E.; Kim, D. J.; Litichevskyi, V.; Mieskolainen, M. M.; Orava, R.; Parkkila, J. E.; Rak, J.; Räsänen, S. S.; Saarinen, S.; Slupecki, M.; Snellman, T. W.; Trzaska, W. H.; Vargyas, M.; Viinikainen, J. (2018)
    Inclusive J/psi production is studied in p-Pb interactions at a centre-of-mass energy per nucleon-nucleon collision root s(NN) = 8.16 TeV, using the ALICE detector at the CERN LHC. The J/psi meson is reconstructed, via its decay to a muon pair, in the centreof-mass rapidity intervals 2.03 < Y-cms < 3.53 and -4.46 < Y-cms < -2.96, where positive and negative Y(cms )refer to the p-going and Pb-going direction, respectively. The transverse momentum coverage is PT < 20 GeV/c. In this paper, Y-cms- and P-T-differential cross sections for inclusive J/psi production are presented, and the corresponding nuclear modification factors R-pPb are shown. Forward results show a suppression of the J/psi yield with respect to pp collisions, concentrated in the region P-T less than or similar to 5 GeV/c. At backward rapidity no significant suppression is observed. The results are compared to previous measurements by ALICE in p-Pb collisions at root s(NN) = 5.02 TeV and to theoretical calculations. Finally, the ratios R-FB between forward- and backward-Y-cms R-pPb values are shown and discussed.
  • The ALICE collaboration; Acharya, S.; Brucken, E. J.; Chang, B.; Hilden, T. E.; Kim, D. J.; Litichevskyi, V.; Mieskolainen, M. M.; Orava, R.; Parkkila, J. E.; Rak, J.; Räsänen, S. S.; Saarinen, S.; Slupecki, M.; Snellman, T. W.; Trzaska, W. H.; Vargyas, M.; Viinikainen, J. (2018)
    The elliptic (v(2)), triangular (v(3)), and quadrangular (v(4)) flow coefficients of pi(+/-), K-+/-, p + (p) over bar, Lambda + (Lambda) over bar, K-S(0)), and the phi-meson are measured in Pb-Pb collisions at root(NN)-N-s = 5.02 TeV. Results obtained with the scalar product method are reported for the rapidity range vertical bar y vertical bar < 0.5 as a function of transverse momentum, P-T, at different collision centrality intervals between 0-70%, including ultra-central (0-1%) collisions for pi(+/-), K-+/-, and p + (p) over bar. For P-T < 3 GeV/c, the flow coefficients exhibit a particle mass dependence. At intermediate transverse momenta (3 < p(T) < 8-10 GeV/c), particles show an approximate grouping according to their type (i.e., mesons and baryons). The phi-meson v(2), which tests both particle mass dependence and type scaling, follows p + <(p)over bar> v(2) at low P-T and pi(+/-) v(2) at intermediate p(T). The evolution of the shape of v(n) (p(T)) as a function of centrality and harmonic number n is studied for the various particle species. Flow coefficients of pi(+/-), K-+/- , and p + (p) over bar for p(T) < 3 GeV/c are compared to iEBE-VISHNU and MUSIC hydrodynamical calculations coupled to a hadronic cascade model (UrQMD). The iEBE-VISHNU calculations describe the results fairly well for P-T < 2.5 GeV/c, while MUSIC calculations reproduce the measurements for p(T) < 1 GeV/c. A comparison to vn coefficients measured in Pb-Pb collisions at root(NN)-N-s = 2.76 TeV is also provided.
  • Ketola, Mikko Juhana (2018)
  • The ALICE collaboration; Acharya, S.; Brucken, E. J.; Chang, B.; Hilden, T. E.; Kim, D. J.; Litichevskyi, V.; Mieskolainen, M. M.; Orava, R.; Parkkila, J. E.; Rak, J.; Räsänen, S. S.; Saarinen, S.; Slupecki, M.; Snellman, T. W.; Trzaska, W. H.; Vargyas, M.; Viinikainen, J. (2018)
    We report on the measurement of the inclusive J/psi polarization parameters in pp collisions at a center of mass energy root s = 8 TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb(-1) J/psi resonances are reconstructed in their di-muon decay channel in the rapidity interval 2.5 < y < 4.0 and over the transverse-momentum interval 2 < pT < 15 GeV/c. The three polarization parameters (lambda(theta), lambda(phi), lambda(theta phi)) are measured as a function of pT both in the helicity and Collins-Soper reference frames. The measured J/psi polarization parameters are found to be compatible with zero within uncertainties, contrary to expectations from all available predictions. The results are compared with the measurement in pp collisions at root s = 7 TeV.
  • The ALICE collaboration; Acharya, S.; Brucken, E. J.; Chang, B.; Kim, D. J.; Litichevskyi, V.; Mieskolainen, M. M.; Orava, R.; Rak, J.; Räsänen, S. S.; Saarinen, S.; Slupecki, M.; Snellman, T. W.; Trzaska, W. H.; Vargyas, M.; Viinikainen, J. (2018)
    Neutral pion and eta meson invariant differential yields were measured in non-single diffractive p-Pb collisions at root S-NN = 5.02 TeV with the ALICE experiment at the CERN LHC. The analysis combines results from three complementary photon measurements, utilizing the PHOS and EMCal calorimeters and the Photon Conversion Method. The invariant differential yields of pi(0) and eta meson inclusive production are measured near mid-rapidity in a broad transverse momentum range of 0.3 < p(T) < 20 GeV/c and 0.7 < p(T) < 20 GeV/c, respectively. The measured eta/pi(0) ratio increases with p(T) and saturates for p(T) > 4 GeV/c at 0.483 +/- 0.015(stat) +/- 0.015(sys). A deviation from m(T) scaling is observed for p(T) < 2 GeV/c. The measured eta/pi(0) ratio is consistent with previous measurements from proton-nucleus and pp collisions over the full pi range. The measured eta/pi(0) ratio at high p(T) also agrees within uncertainties with measurements from nucleus nucleus collisions. The pi(0) and eta yields in p-Pb relative to the scaled pp interpolated reference, R-pPb, are presented for 0.3 < p(T) < 20 GeV/c and 0.7 < p(T) < 20 GeV/c, respectively. The results are compared with theoretical model calculations. The values of R-pPb are consistent with unity for transverse momenta above 2 GeV/c. These results support the interpretation that the suppressed yield of neutral mesons measured in Pb-Pb collisions at LHC energies is due to parton energy loss in the hot QCD medium.
  • Koistinen, Timo (2017)
    In the contemporary Anglo-American philosophy of religion the problem of evil is one of the most widely discussed questions. In the context of these discussions, many prominent philosophers of religion have tried to offer a plausible - or, at least, a possible - explanation why an omnipotent and perfectly good being allows evil in the world and is also morally justified in doing that. There are also philosophers and theologians who think that this way of thinking is seriously misguided. In my paper I will deal with some ethical, theological/ metaphysical and meta-philosophical arguments that have been offered against conceptual frameworks used in the discussion of theodicy. In particular, I will pay attention to affinities and differences between the ways D.Z. Phillips and Brian Davies have criticized contemporary forms of theodicy. I will also analyse the relation between their thought by taking up the question of the nature and aim of philosophy of religion.
  • The ALICE collaboration; Acharya, S.; Brucken, E. J.; Chang, B.; Kim, D. J.; Litichevskyi, V.; Mieskolainen, M. M.; Orava, R.; Rak, J.; Räsänen, S. S.; Saarinen, S.; Slupecki, M.; Snellman, T. W.; Trzaska, W. H.; Vargyas, M.; Viinikainen, J. (2018)
    The production of the charm-strange baryon Xi(0)(c) is measured for the first time at the LHC via its semileptonic decay into e(+) Xi(-) nu(e) in ppcollisions at root s = 7 TeV with the ALICE detector. The transverse momentum ( p(T)) differential cross section multiplied by the branching ratio is presented in the interval 1 < p(T)< 8 GeV/c at mid-rapidity, vertical bar y vertical bar < 0.5. The transverse momentum dependence of the Xi(0)(c) baryon production relative to the D-0 meson production is compared to predictions of event generators with various tunes of the hadronisation mechanism, which are found to underestimate the measured cross-section ratio. (C) 2018 The Author(s). Published by Elsevier B.V.
  • Herrmans, Runa Isabell (2017)
    This article explores the negotiation of permeable personhood and human health and well-being in the healing rituals (belian) of the Luangans, a group of indigenous people of Indonesian Borneo. I describe different techniques employed in the rituals relating to the soul and other components of the self and to extraneous, unbound spirit agencies. Luangan rituals express a relational ontology according to which the constitution of personhood and human well-being is based on the condition of the notoriously volatile human soul or life-force (juus) and the nature of social relations with human and nonhuman beings. Rituals most centrally seek to advance well-being by increasing the fixity and hardness of souls and by improving the relationship with spirits and humans. These efforts are closely interconnected; the condition of the soul is inextricably bound up with the condition of relations with others. This entails a constitutively dual and contextually variable aspiration to both reinforce and open up the boundaries of persons and to associate and dissociate with others. While well-being is generally contingent on containing the soul within the body and alleviating the harmful influence on it of spirits and other humans, it is also adversely affected by alienation and neglect of relations and obligations, and dependent on the help of spirits and human shamans and consociates. The article describes the ambiguous and convoluted nature of Luangan human-spirit relations and how the unpredictability of these relations and the volatility of the soul is reflected in the structure of ritual performances.
  • Macharey, Georg; Väisänen-Tommiska, Mervi; Gissler, Mika; Ulander, Veli-Matti; Rahkonen, Leena; Nuutila, Mika; Heinonen, Seppo (2018)

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