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Baszczyk, M.

Publications and source records attributed to Baszczyk, M..

70 records · Page 4
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DOE OSTI2017

Measurement of the B ± production asymmetry and the C P asymmetry in B ± → J / ψ K ± decays

The B ± meson production asymmetry in pp collisions is measured using B + →¯D 0 π + decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at center-of-mass energies of √s = 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range 2 < p T < 30 GeV/c, and rapidities in the range 2.1 < y < 4.5 are measured to be A prod (B + ,√s = 7 TeV)=(–0.41±0.49±0.10)×10 –2 , A prod (B + ,√s = 8 TeV)=(–0.53±0.31±0.10)×10 –2 , where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of B + →J/ψK + decays, thus allowing a measurement of the CP asymmetry, A CP (B + →J/ψK + )=(0.09±0.27±0.07)×10 –2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the phase difference between short- and long-distance amplitudes in the ${{B} ^+} \!\rightarrow {{{K}} ^+} {\mu ^+\mu ^-} $ decay

A measurement of the phase difference between the short- and long-distance contributions to the B + →K + μ + μ - decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3 fb -1 collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the B + →K + μ + μ - decay is modelled as a sum of relativistic Breit–Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the J /ψ and ψ(2 S ) resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, C 9 and C 10 , and the branching fraction of the short-distance component is measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of B c + → D 0 K + Decays

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb -1 , recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the $B_c^+$ → $D^0K^+$ decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to $B^+$ → $\bar{D}^0π^+$ decays, a measurement of the branching fraction multiplied by the production rates for $B_c^+$ relative to B + mesons in the LHCb acceptance is obtained, $R_{D^0K}$ = ($f_c / f_u$) x $B$($B^+_c$ → $D^0K^+$) = ($9.3_{-2.5}^{+2.8}$ ± 0.6) × 10 -7 , where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first $B^+_c$ decay of this nature to be observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the ratio of branching fractions and difference in CP asymmetries of the decays $B^+$ → $J/ψπ^+$ and $B^+$ → $J/ψK^+$

The ratio of branching fractions and the difference in $CP$ asymmetries of the decays $B^+$ → $J/ψπ^+$ and $B^+$ → $J/ψK^+$ are measured using a data sample of $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 3 fb -1 at centre-of-mass energies of 7 and 8 TeV. The results are B ( B + &#x2192;<!-- → --> J / &#x03C8;<!-- ψ --> &#x03C0;<!-- π --> + ) B ( B + &#x2192;<!-- → --> J / &#x03C8;<!-- ψ --> K + ) = ( 3.83 &#x00B1;<!-- ± --> 0.03 &#x00B1;<!-- ± --> 0.03 ) &#x00D7;<!-- × --> 10 &#x2212;<!-- - --> 2 , A C P ( B + &#x2192;<!-- → --> J / &#x03C8;<!-- ψ --> &#x03C0;<!-- π --> + ) &#x2212;<!-- - --> A C P ( B + &#x2192;<!-- → --> J / &#x03C8;<!-- ψ --> K + ) = ( 1.82 &#x00B1;<!-- ± --> 0.86 &#x00B1;<!-- ± --> 0.14 ) &#x00D7;<!-- × --> 10 &#x2212;<!-- - --> 2 , where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of $A^{CP}$ ($B^+$ → $J/ ψK^+$) provides the most precise estimate to date of $CP$ violation in the decay $B^+$ → $J/ψπ^+$, A C P ( B + &#x2192;<!-- → --> J / &#x03C8;<!-- ψ --> &#x03C0;<!-- π --> + ) = ( 1.91 &#x00B1;<!-- ± --> 0.89 &#x00B1;<!-- ± --> 0.16 ) &#x00D7;<!-- × --> 1 0 &#x2212;<!-- - --> 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for decays of neutral beauty mesons into four muons

A search for the non-resonant decays B s 0 → μ + μ – μ + μ – and B 0 → μ + μ – μ + μ – is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of 1 and 2 fb –1 collected at centre-of-mass energies of 7 and 8 TeV, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at 95% confidence level are determined to be $\mathcal{B}$ (B$^{0}_{s}$→μ + μ – μ + μ – )< 2.5 × 10 –9 , (B 0 →μ + μ – μ + μ – )< 6.9 × 10 –10 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the Annihilation Decay Mode B 0 → K + K –

A search for the B 0 → K + K - decay is performed using pp -collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0 fb -1 at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the $B^{0}_{s}$ → π + π - decay. The measured branching fractions are $\mathcal{B}$(B 0 → K + K - ) = (7.80 ± 1.27 ± 0.81 ± 0.21) × 10 -8 and $\mathcal{B}$(B$^{0}_{s}$ → π + π - ) = (6.91 ± 0.54 ± 0.63 ± 0.19 ± 0.40) × 10 -7 . The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B 0 → K + π - branching fraction used as a normalization. For the $B^{0}_{s}$ mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into $B^{0}_{s}$ and $B^0$ mesons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of CP asymmetry in D 0 → K - K + decays

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D 0 → K - K + is performed using pp collision data, corresponding to an integrated luminosity of 3 fb -1 , collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D *+ →D 0 π + and D* - →$\bar{D}$ 0 π - decays. The time-integrated CP asymmetry A CP (K - K + ) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D 0 →K - π + , D + →K - π + π + and D + →$\bar{K}$ 0 π + decays used as calibration channels. It is found to be A CP (K - K + )=(0.14±0.15 (stat)±0.10 (syst))%. A combination of this result with previous LHCb measurements yields A CP (K - K + )=(0.04±0.12 (stat)±0.10 (syst))%, A CP (π - π + )=(0.07±0.14 (stat)±0.11 (syst))%. These are the most precise measurements from a single experiment. The result for A CP (K - K + ) is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the b -Quark Production Cross Section in 7 and 13 TeV p p Collisions

Measurements of the cross section for producing b quarks in the reaction pp→bbX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2 < η < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered η range are 72.0±0.3±6.8 and 154.3±1.5±14.3 μb for 7 and 13 TeV. The ratio is 2.14±0.02±0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower η than the model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of forward t t - , W + b b ¯ and W + c c ¯ production in pp collisions at s = 8 TeV

The production of $t\bar{t}$, W + $b\bar{b}$ and W + $c\bar{c}$ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb -1 . The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the decay B s 0 → Φ π + π – and evidence for B 0 → Φ π + π –

The first observation of the rare decay B 0 s →Φπ + π – and evidence for B 0 →Φπ + π – are reported, using pp collision data recorded by the LHCb detector at center-of-mass energies √s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . The branching fractions in the π + π – invariant mass range 400 < m(π + π – ) < 1600 MeV/c 2 are [3.48±0.23±0.17±0.35]×10 –6 and [1.82±0.25±0.41±0.14]×10 –7 for B 0 s →Φπ + π – and B 0 →Φπ + π – respectively, where the uncertainties are statistical, systematic and from the normalization mode B 0 s →ΦΦ. A combined analysis of the π + π – mass spectrum and the decay angles of the final-state particles identifies the exclusive decays B 0 s →Φf 0 (980), B 0 s →Φf 2 (1270), and B 0 s →Φρ 0 with branching fractions of [1.12±0.16+0.09–0.08±0.11]×10 –6 , [0.61±0.13+0.12–0.05±0.06]×10 –6 and [2.7±0.7±0.2±0.2]×10 –7 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

First Experimental Study of Photon Polarization in Radiative B s 0 Decays

The polarization of photons produced in radiative B 0 s decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3 fb –1 at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B 0 s →Φγ decay rate is conducted to determine the parameter A Δ , which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A Δ = –0.98 +0.46 –0.52 +0.23 –0.20 is measured. This result is consistent with the standard model prediction within 2 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for the CP-violating strong decays η → π + π - and η' (958)→ π + π -

A search for the CP-violating strong decays η→π + π - and η'(958)→π + π - has been performed using approximately 2.5×10 7 events of each of the decays D + →π + π + π - and D$+\atop{s}$→π + π + π - , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb -1 of pp collision data recorded during LHC Run 1 and 0.3 fb -1 recorded in Run 2. No evidence is seen for D$+\atop{s}$→π + η(') with η(')→π + π - , and upper limits at 90% confidence level are set on the branching fractions, B(η→π + π - )<1.6×10 -5 and B(η'→π + π - )<1.8×10 -5 . The limit for the η decay is comparable with the existing one, while that for the η' is a factor of three smaller than the previous limit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of C P Violation in B 0 → D + D – Decays

The CP violation observables S and C in the decay channel B 0 →D + D – are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb –1 . The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S = –0.54 +0.17 –0.16 (stat)±0.05(syst), C = 0.26 +0.18 –0.17 (stat)±0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of ΔΦ = –0.16 +0.19 –0.21 rad.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Differential branching fraction and angular moments analysis of the decay B 0 → K + π - μ + μ - in the K 0,2 * (1430)⁰ region

Here, measurements of the differential branching fraction and angular moments of the decay B 0 → K + π - μ + μ - in the K + π - invariant mass range 1330 < m(K + π - ) < 1530 MeV/c 2 are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb -1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q 2 , between 0.1 and 8.0 GeV 2 /c 4 . For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q 2 range 1.1-6.0 GeV 2 /c 4 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗