ORCID Profile
0000-0003-0062-1985
Current Organisations
European Organization for Nuclear Research
,
Institute of Nuclear Physics
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Publisher: American Physical Society (APS)
Date: 22-09-2020
Publisher: American Physical Society (APS)
Date: 20-04-2022
Publisher: Springer Science and Business Media LLC
Date: 10-2020
Abstract: Searches are performed for a low-mass dimuon resonance, X , produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data s le corresponding to an integrated luminosity of 5.1 fb − 1 and collected with the LHCb detector. The X bosons can either decay promptly or displaced from the proton-proton collision, where in both cases the requirements placed on the event and the assumptions made about the production mechanisms are kept as minimal as possible. The searches for promptly decaying X bosons explore the mass range from near the dimuon threshold up to 60 GeV, with nonnegligible X widths considered above 20 GeV. The searches for displaced X → μ + μ − decays consider masses up to 3 GeV. None of the searches finds evidence for a signal and 90% confidence-level exclusion limits are placed on the X → μ + μ − cross sections, each with minimal model dependence. In addition, these results are used to place world-leading constraints on GeV-scale bosons in the two-Higgs-doublet and hidden-valley scenarios.
Publisher: American Physical Society (APS)
Date: 25-05-2022
Publisher: American Physical Society (APS)
Date: 20-02-2020
Publisher: American Physical Society (APS)
Date: 04-06-2020
Publisher: Springer Science and Business Media LLC
Date: 06-05-2022
Abstract: The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 . 4 fb − 1. The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is reconstructed partially, where the photon from the $$ {\\varXi}_c^{\\prime +}\\to {\\varXi}_c^{+}\\gamma $$ Ξ c ′ + → Ξ c + γ decay is not reconstructed and the pK − π + final state of the $$ {\\varXi}_c^{+} $$ Ξ c + baryon is employed. The $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{\\prime +}{\\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + branching fraction relative to that of the $$ {\\varXi}_{cc}^{++}\\to {\\varXi}_c^{+}{\\pi}^{+} $$ Ξ cc + + → Ξ c + π + decay is measured to be 1 . 41 ± 0 . 17 ± 0 . 10, where the first uncertainty is statistical and the second systematic.
Publisher: American Physical Society (APS)
Date: 07-12-2020
Publisher: Springer Science and Business Media LLC
Date: 08-04-2022
Abstract: A study of B + → J / ψηK + decays, followed by J / ψ → μ + μ − and η → γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The J / ψη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B + → (ψ 2 (3823) → J / ψη)K + and B + → (ψ(4040) → J / ψη)K + decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the ψ 2 (3823) → J / ψη decay.
Publisher: American Physical Society (APS)
Date: 06-01-2021
Publisher: Springer Science and Business Media LLC
Date: 08-2020
Abstract: The decays B + → J / ψπ + π − K + are studied using a data set corresponding to an integrated luminosity of 9 fb − 1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ 2 (3823), χ c1 (3872) and ψ(2S) states are reported. The values are $$ {\\displaystyle \\begin{array}{c}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.56\\pm 0.67\\pm 0.11\\right)\\times {10}^{-2},\\\\ {}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(1.31\\pm 0.25\\pm 0.04\\right)\\times {10}^{-3},\\\\ {}\\frac{{\\mathcal{B}}_{\\mathrm{B}+\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.69\\pm 0.07\\pm 0.06\\right)\\times {10}^{-2},\\end{array}} $$ B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − = 3.56 ± 0.67 ± 0.11 × 10 − 2 , B B + → ψ 2 3823 K + × B ψ 2 3823 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 1.31 ± 0.25 ± 0.04 × 10 − 3 , B B + → χ c 1 3872 K + × B χ c 1 3872 → J / ψπ + π − B B + → ψ 2 S K + × B ψ 2 S → J / ψπ + π − = 3.69 ± 0.07 ± 0.06 × 10 − 2 , where the first uncertainty is statistical and the second is systematic. The decay of B + → ψ 2 (3823)K + with ψ 2 (3823) → J / ψπ + π − is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ 2 (3823), χ c1 (3872) and ψ(2S) states are measured to be $$ {\\displaystyle \\begin{array}{c}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2(3823)}=47.50\\pm 0.53\\pm 0.13\\ \\mathrm{MeV}/{c}^2,\\\\ {}{m}_{\\uppsi_2(3823)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=137.98\\pm 0.53\\pm 0.14\\ \\mathrm{MeV}/{c}^2,\\\\ {}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=185.49\\pm 0.06\\pm 0.03\\ \\mathrm{MeV}/{c}^2,\\end{array}} $$ m χ c 1 3872 − m ψ 2 3823 = 47.50 ± 0.53 ± 0.13 MeV / c 2 , m ψ 2 3823 − m ψ 2 2 S = 137.98 ± 0.53 ± 0.14 MeV / c 2 , m χ c 1 3872 − m ψ 2 2 S = 185.49 ± 0.06 ± 0.03 MeV / c 2 , resulting in the most precise determination of the χ c1 (3872) mass. The width of the ψ 2 (3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χ c1 (3872) state is measured to be $$ {\\Gamma}_{\\upchi_{\\mathrm{c}1}(3872)}^{\\mathrm{BW}}={0.96}_{-0.18}^{+0.19}\\pm 0.21\\ \\mathrm{MeV} $$ Γ χ c 1 3872 BW = 0.96 − 0.18 + 0.19 ± 0.21 MeV which is inconsistent with zero by 5.5 standard deviations.
Publisher: Elsevier BV
Date: 12-2020
Publisher: Springer Science and Business Media LLC
Date: 2020
DOI: 10.1140/EPJC/S10052-019-7486-9
Abstract: This erratum corrects measurements of the prompt and secondary (from- b ).
Publisher: Springer Science and Business Media LLC
Date: 10-2020
DOI: 10.1140/EPJC/S10052-020-8365-0
Abstract: A first search for $$CP$$ CP violation in the Cabibbo-suppressed $${{{\\varXi }} ^+_{c}} \\rightarrow {p} {{K} ^-} {{\\pi } ^+} $$ Ξ c + → p K - π + decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a s le of proton-proton collision data, corresponding to an integrated luminosity of $$3.0\\,\\text {fb} ^{-1} $$ 3.0 fb - 1 , and collected by the LHCb experiment at centre-of-mass energies of 7 and $$8\\,\\text {TeV} $$ 8 TeV . The data are consistent with the hypothesis of no $$CP$$ CP violation.
Publisher: American Physical Society (APS)
Date: 02-03-2021
Publisher: American Physical Society (APS)
Date: 12-11-2020
Publisher: American Physical Society (APS)
Date: 12-10-2020
Publisher: American Physical Society (APS)
Date: 07-12-2020
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: The CKM angle γ is measured for the first time from mixing-induced CP violation between $$ {B}_s^0\\to {D}_s^{\\mp }{K}^{\\pm }{\\pi}^{\\pm }{\\pi}^{\\mp } $$ B s 0 → D s ∓ K ± π ± π ∓ and $$ {\\overline{B}}_s^0\\to {D}_s^{\\pm }{K}^{\\mp }{\\pi}^{\\mp }{\\pi}^{\\pm } $$ B ¯ s 0 → D s ± K ∓ π ∓ π ± decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 fb − 1 recorded with the LHCb detector. A time-dependent litude analysis is performed to extract the CP -violating weak phase γ − 2 β s and, subsequently, γ by taking the $$ {B}_s^0\\hbox{-} {\\overline{B}}_s^0 $$ B s 0 ‐ B ¯ s 0 mixing phase β s as an external input. The measurement yields γ = (44 ± 12)° modulo 180°, where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields $$ \\gamma =\\left({44}_{-13}^{+20}\\right){}^{\\circ} $$ γ = 44 − 13 + 20 ° modulo 180°. Moreover, the $$ {B}_s^0\\hbox{-} {\\overline{B}}_s^0 $$ B s 0 ‐ B ¯ s 0 oscillation frequency is measured from the flavour-specific control channel $$ {B}_s^0\\to {D}_s^{-}{\\pi}^{+}{\\pi}^{+}{\\pi}^{-} $$ B s 0 → D s − π + π + π − to be ∆ m s = (17 . 757 ± 0 . 007(stat) ± 0 . 008(syst)) ps − 1 , consistent with and more precise than the current world-average value.
Publisher: American Physical Society (APS)
Date: 22-12-2020
Publisher: Springer Science and Business Media LLC
Date: 11-05-2022
Abstract: A search for the decay B 0 → ϕμ + μ − is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb − 1 . No evidence for the B 0 → ϕμ + μ − decay is found and an upper limit on the branching fraction, excluding the ϕ and charmonium regions in the dimuon spectrum, of 4 . 4 × 10 − 3 at a 90% credibility level, relative to that of the $$ {B}_s^0 $$ B s 0 → ϕμ + μ − decay, is established. Using the measured $$ {B}_s^0 $$ B s 0 → ϕμ + μ − branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B 0 → ϕμ + μ − in the full q 2 range is determined to be less than 3 . 2 × 10 − 9 at a 90% credibility level.
Publisher: Springer Science and Business Media LLC
Date: 03-2021
Abstract: The time-dependent CP asymmetries of B 0 → π + π − and $$ {B}_s^0 $$ B s 0 → K + K − decays are measured using a data s le of pp collisions corresponding to an integrated luminosity of 1.9 fb − 1 , collected with the LHCb detector at a centre-of-mass energy of 13 TeV. The results are $$ {\\displaystyle \\begin{array}{c}{C}_{\\pi \\pi}=-0.311\\pm 0.045\\pm 0.015,\\\\ {}{S}_{\\pi \\pi}=-0.706\\pm 0.042\\pm 0.013,\\\\ {}{C}_{KK}=0.123\\pm 0.034\\pm 0.015,\\\\ {}{S}_{KK}=0.164\\pm 0.034\\pm 0.014,\\\\ {}{\\mathcal{A}}_{KK}^{\\Delta \\varGamma }=-0.83\\pm 0.05\\pm 0.09,\\end{array}} $$ C ππ = − 0.311 ± 0.045 ± 0.015 , S ππ = − 0.706 ± 0.042 ± 0.013 , C KK = 0.123 ± 0.034 ± 0.015 , S KK = 0.164 ± 0.034 ± 0.014 , A KK Δ Γ = − 0.83 ± 0.05 ± 0.09 , where the first uncertainties are statistical and the second systematic. The same data s le is used to measure the time-integrated CP asymmetries of B 0 → K + π − and $$ {B}_s^0 $$ B s 0 → K − π + decays and the results are $$ {\\displaystyle \\begin{array}{c}{A}_{CP}^{B^0}=-0.0824\\pm 0.0033\\pm 0.0033,\\\\ {}{A}_{CP}^{B_s^0}=0.236\\pm 0.013\\pm 0.011.\\end{array}} $$ A CP B 0 = − 0.0824 ± 0.0033 ± 0.0033 , A CP B s 0 = 0.236 ± 0.013 ± 0.011 . All results are consistent with earlier measurements. A combination of LHCb measurements provides the first observation of time-dependent CP violation in $$ {B}_s^0 $$ B s 0 decays.
Publisher: American Physical Society (APS)
Date: 18-12-2020
Publisher: Springer Science and Business Media LLC
Date: 02-2021
Abstract: The decays $$ {\\mathrm{B}}_{\\mathrm{s}}^0 $$ B s 0 → J / ψπ + π − K + K − are studied using a data set corresponding to an integrated luminosity of 9 fb − 1 , collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays $$ {\\mathrm{B}}_{\\mathrm{s}}^0 $$ B s 0 → $$ \\mathrm{J}/{\\uppsi \\mathrm{K}}^{\\ast 0}{\\overline{\\mathrm{K}}}^{\\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 and $$ {\\mathrm{B}}_{\\mathrm{s}}^0 $$ B s 0 → χ c1 (3872)K + K − , where the K + K − pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χ c1 (3872)ϕ, $$ \\mathrm{J}/{\\uppsi \\mathrm{K}}^{\\ast 0}{\\overline{\\mathrm{K}}}^{\\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 , ψ(2S)ϕ and χ c1 (3872)K + K − states are reported. A structure, denoted as X(4740), is observed in the J / ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be $$ {\\displaystyle \\begin{array}{c}{m}_{\\mathrm{X}(4740)}=4741\\pm 6\\pm 6\\kern0.5em \\mathrm{MeV}/{c}^2,\\\\ {}{\\Gamma}_{\\mathrm{X}(4740)}=53\\pm 15\\pm 11\\kern0.5em \\mathrm{MeV},\\end{array}} $$ m X 4740 = 4741 ± 6 ± 6 MeV / c 2 , Γ X 4740 = 53 ± 15 ± 11 MeV , where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the $$ {\\mathrm{B}}_{\\mathrm{s}}^0 $$ B s 0 meson is performed and gives a value of $$ {m}_{{\\mathrm{B}}_{\\mathrm{s}}^0}=5366.98\\pm 0.07\\pm 0.13\\kern0.5em \\mathrm{MeV}/{c}^2. $$ m B s 0 = 5366.98 ± 0.07 ± 0.13 MeV / c 2 .
Publisher: Springer Science and Business Media LLC
Date: 02-2021
Abstract: A measurement of CP -violating observables is performed using the decays B ± → DK ± and B ± → Dπ ± , where the D meson is reconstructed in one of the self-conjugate three-body final states $$ {K}_{\\mathrm{S}}^0 $$ K S 0 π + π − and $$ {K}_{\\mathrm{S}}^0 $$ K S 0 K + K − (commonly denoted $$ {K}_{\\mathrm{S}}^0 $$ K S 0 h + h − ). The decays are analysed in bins of the D -decay phase space, leading to a measurement that is independent of the modelling of the D -decay litude. The observables are inter- preted in terms of the CKM angle γ . Using a data s le corresponding to an integrated luminosity of 9 fb − 1 collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, γ is measured to be $$ \\left({68.7}_{-5.1}^{+5.2}\\right){}^{\\circ} $$ 68.7 − 5.1 + 5.2 ° . The hadronic parameters $$ {r}_B^{D K},{r}_B^{D\\pi},{\\delta}_B^{D K},\\kern0.5em \\mathrm{and}\\kern0.5em {\\delta}_B^{D\\pi} $$ r B DK , r B Dπ , δ B DK , and δ B Dπ , which are the ratios and strong-phase differences of the suppressed and favoured B ± decays, are also reported.
Publisher: American Physical Society (APS)
Date: 31-07-2020
Publisher: Springer Science and Business Media LLC
Date: 12-2020
Abstract: The shape of the $$ {B}_s^0\\to {D}_s^{\\ast -}{\\mu}^{+}{\\nu}_{\\mu } $$ B s 0 → D s ∗ − μ + ν μ differential decay rate is obtained as a function of the hadron recoil parameter using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.7 fb − 1 collected by the LHCb detector. The $$ {B}_s^0\\to {D}_s^{\\ast -}{\\mu}^{+}{\\nu}_{\\mu } $$ B s 0 → D s ∗ − μ + ν μ decay is reconstructed through the decays $$ {D}_s^{\\ast -}\\to {D}_s^{-}\\gamma $$ D s ∗ − → D s − γ and $$ {D}_s^{-}\\to {K}^{-}{K}^{+}{\\pi}^{-} $$ D s − → K − K + π − . The differential decay rate is fitted with the Caprini-Lellouch-Neubert (CLN) and Boyd-Grinstein-Lebed (BGL) parametrisations of the form factors, and the relevant quantities for both are extracted.
Publisher: Springer Science and Business Media LLC
Date: 11-2020
Abstract: A search for the doubly heavy $$ {\\Xi}_{bc}^0 $$ Ξ bc 0 baryon using its decay to the D 0 pK – final state is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb − 1 . No significant signal is found in the invariant mass range from 6.7 to 7.2 GeV/ c 2 . Upper limits are set at 95% credibility level on the ratio of the $$ {\\Xi}_{bc}^0 $$ Ξ bc 0 production cross-section times its branching fraction to D 0 pK − relative to that of the $$ {\\Lambda}_b^0\\to {D}^0{pK}^{-} $$ Λ b 0 → D 0 pK − decay. The limits are set as a function of the $$ {\\Xi}_{bc}^0 $$ Ξ bc 0 mass and lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and in the transverse momentum region from 5 to 25 GeV/ c . Upper limits range from 1 . 7 × 10 − 2 to 3 . 0 × 10 − 1 for the considered $$ {\\Xi}_{bc}^0 $$ Ξ bc 0 mass and lifetime hypotheses.
Publisher: American Physical Society (APS)
Date: 05-03-2021
Publisher: IOP Publishing
Date: 04-2021
Abstract: A search for the rare decay is performed using collision data collected with the LHCb dete-ctor at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb −1 . No significant signal of the decay is observed and an upper limit of at 90% confidence level is set on the branching fraction.
Publisher: American Physical Society (APS)
Date: 13-05-2022
Publisher: Springer Science and Business Media LLC
Date: 12-2020
Abstract: An angular analysis of the B 0 → K* 0 e + e − decay is performed using a data s le corresponding to an integrated luminosity of 9 fb − 1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared ( q 2 ) interval between 0 . 0008 and 0 . 257 GeV 2 , where the rate is dominated by the B 0 → K * 0 γ transition with a virtual photon. The fraction of longitudinal polarisation of the K * 0 meson, F L , is measured to be F L = (4 . 4 ± 2 . 6 ± 1 . 4)%, where the first uncertainty is statistical and the second systematic. The $$ {A}_{\\mathrm{T}}^{\\mathrm{Re}} $$ A T Re observable, which is related to the lepton forward-backward asymmetry, is measured to be $$ {A}_{\\mathrm{T}}^{\\mathrm{Re}} $$ A T Re = − 0 . 06 ± 0 . 08 ± 0 . 02. The $$ {A}_{\\mathrm{T}}^{(2)} $$ A T 2 and $$ {A}_{\\mathrm{T}}^{\\mathrm{Im}} $$ A T Im transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be $$ {A}_{\\mathrm{T}}^{(2)} $$ A T 2 = 0 . 11 ± 0 . 10 ± 0 . 02 and $$ {A}_{\\mathrm{T}}^{\\mathrm{Im}} $$ A T Im = 0 . 02 ± 0 . 10 ± 0 . 01. The results are consistent with Standard Model predictions and provide the world’s best constraint on the b → sγ photon polarisation.
Publisher: American Physical Society (APS)
Date: 08-09-2020
Location: Poland
No related grants have been discovered for Bartosz Małecki.