ORCID Profile
0000-0002-6226-957X
Current Organisation
AGH University of Science and Technology
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Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 03-2018
Publisher: Springer Science and Business Media LLC
Date: 06-2018
DOI: 10.1140/EPJC/S10052-018-5950-6
Abstract: The nuclear modification factors of $${\mathrm {J}/\psi }$$ J / ψ and $$\psi \text {(2S)}$$ ψ (2S) mesons are measured in $$\text {PbPb}$$ PbPb collisions at a centre-of-mass energy per nucleon pair of $$\sqrt{\smash [b]{s_{_{\text {NN}}}}} = 5.02\,\text {Te}\text {V} $$ s NN = 5.02 TeV . The analysis is based on $$\text {PbPb}$$ PbPb and $$\mathrm {p}\mathrm {p}$$ p p data s les collected by CMS at the LHC in 2015, corresponding to integrated luminosities of 464 $$\,\mu \mathrm {b}^{-1}$$ μ b - 1 and 28 $$\,\text {pb}^\text {-1}$$ pb -1 , respectively. The measurements are performed in the dimuon rapidity range of $$|y | 2.4$$ | y | 2.4 as a function of centrality, rapidity, and transverse momentum ( $$p_{\mathrm {T}}$$ p T ) from $$p_{\mathrm {T}} =3$$ p T = 3 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c in the most forward region and up to 50 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c . Both prompt and nonprompt (coming from b hadron decays) $${\mathrm {J}/\psi }$$ J / ψ mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at $$\sqrt{\smash [b]{s_{_{\text {NN}}}}} = 2.76\,\text {Te}\text {V} $$ s NN = 2.76 TeV for the two $${\mathrm {J}/\psi }$$ J / ψ meson components. No dependence on rapidity is observed for either prompt or nonprompt $${\mathrm {J}/\psi }$$ J / ψ mesons. An indication of a lower prompt $${\mathrm {J}/\psi }$$ J / ψ meson suppression at $$p_{\mathrm {T}} 25$$ p T 25 $${\,\text {Ge}\text {V}/}\text {c}$$ GeV / c is seen with respect to that observed at intermediate $$p_{\mathrm {T}}$$ p T . The prompt $$\psi \text {(2S)}$$ ψ (2S) meson yield is found to be more suppressed than that of the prompt $${\mathrm {J}/\psi }$$ J / ψ mesons in the entire $$p_{\mathrm {T}}$$ p T range.
Publisher: IOP Publishing
Date: 08-12-2011
Publisher: American Astronomical Society
Date: 10-2020
Abstract: We present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (PSR J0437−4715, PSR J0711−6830, and PSR J0737−3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835−4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their first and second observing runs. For the first time, we are able to match (for PSR J0437−4715) or surpass (for PSR J0711−6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10 −8 . For each of the five pulsars, we perform targeted searches that assume a tight coupling between the gravitational-wave and electromagnetic signal phase evolution. We also present constraints on PSR J0711−6830, the Crab pulsar, and the Vela pulsar from a search that relaxes this assumption, allowing the gravitational-wave signal to vary from the electromagnetic expectation within a narrow band of frequencies and frequency derivatives.
Publisher: Springer Science and Business Media LLC
Date: 07-2020
DOI: 10.1140/EPJC/S10052-020-7917-7
Abstract: Normalised multi-differential cross sections for top quark pair ( $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ ) production are measured in proton-proton collisions at a centre-of-mass energy of 13 $$\\,{\\text {TeV}}$$ TeV using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $$35.9{\\,{\\text {fb}}^{-1}} $$ 35.9 fb - 1 . The double-differential $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ cross section is measured as a function of the kinematic properties of the top quark and of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength $$\\alpha _{S}$$ α S and the top quark pole mass ( $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole ) using several sets of parton distribution functions (PDFs). The measurement of $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole exploits the sensitivity of the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ invariant mass distribution to $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole near the production threshold. Furthermore, a simultaneous fit of the PDFs, $$\\alpha _{S}$$ α S , and $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of $$\\alpha _{S}$$ α S and $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole . The values $$\\alpha _{S}(m_{{\\text {Z}}}) = 0.1135{}^{+0.0021}_{-0.0017}$$ α S ( m Z ) = 0.1135 - 0.0017 + 0.0021 and $$m_{{\\text {t}}}^{{\\text {pole}}} = 170.5 \\pm 0.8 \\,{\\text {GeV}} $$ m t pole = 170.5 ± 0.8 GeV are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $$\\hbox {t}{\\bar{\\hbox {t}}}$$ t t ¯ production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole of the order of $$+1 \\,{\\text {GeV}} $$ + 1 GeV , which can be regarded as additional theoretical uncertainty in the current $$m_{{\\text {t}}}^{{\\text {pole}}}$$ m t pole extraction.
Publisher: American Physical Society (APS)
Date: 24-08-2020
Publisher: American Physical Society (APS)
Date: 22-06-2020
Publisher: American Physical Society (APS)
Date: 02-09-2020
Publisher: Elsevier BV
Date: 09-2012
Publisher: American Physical Society (APS)
Date: 03-09-2020
Publisher: Springer Science and Business Media LLC
Date: 06-2018
Abstract: A search for flavor-changing neutral currents (FCNC) in events with the top quark and the Higgs boson is presented. The Higgs boson decay to a pair of b quarks is considered. The data s le corresponds to an integrated luminosity of 35.9 fb −1 recorded by the CMS experiment at the LHC in proton-proton collisions at $$ \\sqrt{s}=13 $$ s = 13 TeV. Two channels are considered: single top quark FCNC production in association with the Higgs boson (pp → tH), and top quark pair production with FCNC decay of the top quark (t → qH). Final states with one isolated lepton and at least three reconstructed jets, among which at least two are associated with b quarks, are studied. No significant deviation is observed from the predicted background. Observed (expected) upper limits at 95% confidence level are set on the branching fractions of top quark decays, ℬ(t → uH) 0.47% (0.34%) and ℬ(t → cH) 0.47% (0.44%), assuming a single nonzero FCNC coupling.
Publisher: Springer Science and Business Media LLC
Date: 09-2018
DOI: 10.1140/EPJC/S10052-018-6242-X
Abstract: A search is presented for physics beyond the standard model, based on measurements of dijet angular distributions in proton–proton collisions at $$\\sqrt{s}=13\\hbox {TeV}$$ s = 13 TeV . The data collected with the CMS detector at the LHC correspond to an integrated luminosity of 35.9 $$\\,\\text {fb}^{-1}$$ fb - 1 . The observed distributions, corrected to particle level, are found to be in agreement with predictions from perturbative quantum chromodynamics that include electroweak corrections. Constraints are placed on models containing quark contact interactions, extra spatial dimensions, quantum black holes, or dark matter, using the detector-level distributions. In a benchmark model where only left-handed quarks participate, contact interactions are excluded at the 95% confidence level up to a scale of 12.8 or 17.5TeV, for destructive or constructive interference, respectively. The most stringent lower limits to date are set on the ultraviolet cutoff in the Arkani–Hamed–Dimopoulos–Dvali model of extra dimensions. In the Giudice–Rattazzi–Wells convention, the cutoff scale is excluded up to 10.1TeV. The production of quantum black holes is excluded for masses below 5.9 and 8.2TeV, depending on the model. For the first time, lower limits between 2.0 and 4.6TeVare set on the mass of a dark matter mediator for (axial-)vector mediators, for the universal quark coupling $$g_{\\mathrm {\\mathrm {q}}} =1.0$$ g q = 1.0 .
Publisher: Springer Science and Business Media LLC
Date: 13-05-2015
DOI: 10.1038/NATURE14474
Abstract: The standard model of particle physics describes the fundamental particles and their interactions via the strong, electromagnetic and weak forces. It provides precise predictions for measurable quantities that can be tested experimentally. The probabilities, or branching fractions, of the strange B meson (B(s)(0)) and the B0 meson decaying into two oppositely charged muons (μ+ and μ−) are especially interesting because of their sensitivity to theories that extend the standard model. The standard model predicts that the B(s)(0) →µ+µ− and B(0) →µ+µ− decays are very rare, with about four of the former occurring for every billion mesons produced, and one of the latter occurring for every ten billion B0 mesons. A difference in the observed branching fractions with respect to the predictions of the standard model would provide a direction in which the standard model should be extended. Before the Large Hadron Collider (LHC) at CERN started operating, no evidence for either decay mode had been found. Upper limits on the branching fractions were an order of magnitude above the standard model predictions. The CMS (Compact Muon Solenoid) and LHCb (Large Hadron Collider beauty) collaborations have performed a joint analysis of the data from proton–proton collisions that they collected in 2011 at a centre-of-mass energy of seven teraelectronvolts and in 2012 at eight teraelectronvolts. Here we report the first observation of the B(s)(0) → µ+µ− decay, with a statistical significance exceeding six standard deviations, and the best measurement so far of its branching fraction. Furthermore, we obtained evidence for the B(0) → µ+µ− decay with a statistical significance of three standard deviations. Both measurements are statistically compatible with standard model predictions and allow stringent constraints to be placed on theories beyond the standard model. The LHC experiments will resume taking data in 2015, recording proton–proton collisions at a centre-of-mass energy of 13 teraelectronvolts, which will approximately double the production rates of B(s)(0) and B0 mesons and lead to further improvements in the precision of these crucial tests of the standard model.
Publisher: Springer Science and Business Media LLC
Date: 08-2020
DOI: 10.1140/EPJC/S10052-020-8166-5
Abstract: Central exclusive and semiexclusive production of "Equation missing" pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central "Equation missing" production are measured as functions of invariant mass, transverse momentum, and rapidity of the "Equation missing" system in the fiducial region defined as transverse momentum "Equation missing" and pseudorapidity "Equation missing" . The production cross sections for the four resonant channels "Image missing" , "Equation missing" , "Image missing" , and "Image missing" are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13TeV.
Publisher: American Astronomical Society
Date: 20-04-2020
No related grants have been discovered for Krzysztof Piotrzkowski.