arXiv subjects

M. Baszczyk

Publications and source records attributed to M. Baszczyk.

82 records · Page 5Linked to original sources

arXiv2017

First experimental study of photon polarization in radiative $B^{0}_{s}$ 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 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} \to ϕγ$ decay rate is conducted to determine the parameter ${\mathcal{A}}^Δ$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b \to s γ$ transitions. A value of ${\mathcal{A}}^Δ=-0.98^{\,+0.46\,+0.23}_{\,-0.52\,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviations.

hep-ex↗

arXiv2017

Observation of $B^+\rightarrow J/ψ3π^+ 2π^-$ and $B^+\rightarrow ψ(2S) π^+π^+π^-$ decays

The decays $B^+\rightarrow J/ψ3π^+ 2π^-$ and $B^+\rightarrow ψ(2S) π^+π^+π^-$ are observed for the first time using a data sample corresponding to an integrated luminosity of $3.0fb^{-1}$, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. The branching fractions relative to that of $B^+ \rightarrow ψ(2S)K^+$ are measured to be \begin{eqnarray*} \frac {\mathcal{B}\left(B^+\rightarrow J/ψ3π^+ 2π^- \right)} {\mathcal{B}\left(B^+ \rightarrow ψ(2S)K^+ \right)} & = & \left(1.88\pm0.17\pm0.09\right)\times10^{-2}, \frac {\mathcal{B}\left(B^+\rightarrow ψ(2S) π^+π^+π^- \right)} {\mathcal{B}\left(B^+ \rightarrow ψ(2S)K^+ \right)} & = & \left(3.04\pm0.50\pm0.26\right)\times10^{-2}, \end{eqnarray*} where the first uncertainties are statistical and the second are systematic.

hep-ex↗

arXiv2017

Observation of the decay $Ξ_b^- \to p K^-K^-$

Decays of the $Ξ_b^-$ and $Ω_b^-$ baryons to the charmless final states $p h^{-}h^{\prime -}$, where $h^{(\prime)}$ denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at centre-of-mass energies $\sqrt{s} = 7$ and $8 TeV$, corresponding to an integrated luminosity of $3 {\rm fb}^{-1}$. The decay $Ξ_b^- \to p K^-K^-$ is observed with a significance of $8.7$ standard deviations, and evidence at the level of $3.4$ standard deviations is found for the $Ξ_b^- \to p K^-π^-$ decay. Results are reported, relative to the $B^-\to K^+K^-K^-$ normalisation channel, for the products of branching fractions and $b$-hadron production fractions. The branching fractions of $Ξ_b^- \to p K^-π^-$ and $Ξ_b^- \to p π^-π^-$ relative to $Ξ_b^- \to p K^-K^-$ decays are also measured.

hep-ex↗

arXiv2017

Measurement of forward $t\overline{t}$, $W+b\overline{b}$ and $W+c\overline{c}$ production in $pp$ collisions at $\sqrt{s}=8$ TeV

The production of $t\overline{t}$, $W+b\overline{b}$ and $W+c\overline{c}$ 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 $\pm$ 0.02 $\mbox{fb}^{-1}$. The $W$ bosons are reconstructed in the decays $W\rightarrow\ellν$, where $\ell$ 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.

hep-ex↗

arXiv2017

Search for the $C\!P$-violating strong decays $η\to π^+π^-$ and $η^\prime(958) \to π^+π^-$

A search for the $C\!P$-violating strong decays $η\to π^+π^-$ and $η^\prime(958) \to π^+π^-$ has been performed using approximately $2.5 \times 10^{7}$ events of each of the decays $D^+ \to π^+π^+π^-$ and $D_s^+ \to π^+π^+π^-$, 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 $D^+_{(s)} \to π^+ η^{(\prime)}$ with $η^{(\prime)} \to π^+π^-$, and upper limits at 90% confidence level are set on the branching fractions, $\mathcal{B}(η\to π^+π^-) < 1.6 \times 10^{-5}$ and $\mathcal{B}(η^\prime \to π^+π^-) < 1.8 \times 10^{-5}$. The limit for the $η$ decay is comparable with the existing one, while that for the $η^\prime$ is a factor of three smaller than the previous limit.

hep-ex↗

arXiv2017

Measurement of the $B^{\pm}$ production asymmetry and the $CP$ asymmetry in $B^{\pm} \to J/ψK^{\pm}$ decays

The $B^{\pm}$ meson production asymmetry in $pp$ collisions is measured using $B^+ \to \bar{D}^0 π^+$ decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at centre-of-mass energies of $\sqrt{s}=$ 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range $2 < p_{\rm T} < 30$ GeV/$c$, and rapidities in the range $2.1 < y < 4.5$, are measured to be \begin{align*} \mathcal{A}_{\rm prod}(B^+,\sqrt{s}=7~{\rm TeV}) &= (-0.41 \pm 0.49 \pm 0.10) \times 10^{-2},\\ \mathcal{A}_{\rm prod}(B^+,\sqrt{s}=8~{\rm TeV}) &= (-0.53 \pm 0.31 \pm 0.10) \times 10^{-2}, \end{align*} where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of $B^{+} \to J/ψK^{+}$ decays, thus allowing a measurement of the $CP$ asymmetry, \begin{equation*} \mathcal{A}_{CP} = (0.09 \pm 0.27 \pm 0.07) \times 10^{-2}. \end{equation*}

hep-ex↗

arXiv2017

Observation of the decay $B^0_s \to ϕπ^+π^-$ and evidence for $B^0 \to ϕπ^+π^-$

The first observation of the rare decay$B^0_s \to ϕπ^+π^-$ and evidence for $B^0 \to ϕπ^+π^-$ are reported, using $pp$ collision data recorded by the LHCb detector at centre-of-mass energies $\sqrt{s} = 7$ and 8~TeV, corresponding to an integrated luminosity of $3{\mbox{\,fb}^{-1}}$. The branching fractions in the $π^+π^-$ invariant mass range $400<m(π^+π^-)<1600{\mathrm{\,Me\kern -0.1em V\!/}c^2}$ are $[3.48\pm 0.23\pm 0.17\pm 0.35]\times 10^{-6}$ and $[1.82\pm 0.25\pm 0.41\pm 0.14]\times 10^{-7}$ for $B^0_s \to ϕπ^+π^-$ and $B^0 \to ϕπ^+π^-$ respectively, where the uncertainties are statistical, systematic and from the normalisation mode $B^0_s \to ϕϕ$. 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 \to ϕf_0(980) $, $B_s^0 \to ϕf_2(1270) $, and $B^0_s \to ϕρ^0$ with branching fractions of $[1.12\pm 0.16^{+0.09}_{-0.08}\pm 0.11]\times 10^{-6}$, $[0.61\pm 0.13^{+0.12}_{-0.05}\pm 0.06]\times 10^{-6}$ and $[2.7\pm 0.7\pm 0.2\pm 0.2]\times 10^{-7}$, respectively.

hep-ex↗

arXiv2016

Differential branching fraction and angular moments analysis of the decay $B^0 \to K^+ π^- μ^+ μ^-$ in the $K^*_{0,2}(1430)^0$ region

Measurements of the differential branching fraction and angular moments of the decay $B^0 \to K^+ π^- μ^+ μ^-$ 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 $GeV^2/c^4$.

hep-ex↗

arXiv2016

Measurement of the CKM angle $γ$ from a combination of LHCb results

A combination of measurements sensitive to the CKM angle $γ$ from LHCb is performed. The inputs are from analyses of time-integrated $B^{+}\rightarrow DK^+$, $B^{0} \rightarrow D K^{*0}$, $B^{0} \rightarrow D K^+ π^-$ and $B^{+} \rightarrow D K^+π^+π^-$ tree-level decays. In addition, results from a time-dependent analysis of $B_{s}^{0} \rightarrow D_{s}^{\mp}K^{\pm}$ decays are included. The combination yields $γ= (72.2^{+6.8}_{-7.3})^\circ$, where the uncertainty includes systematic effects. The 95.5% confidence level interval is determined to be $γ\in [55.9,85.2]^\circ$. A second combination is investigated, also including measurements from $B^{+} \rightarrow D π^+$ and $B^{+} \rightarrow D π^+π^-π^+$ decays, which yields compatible results.

hep-ex↗

arXiv2013

SuperB Technical Design Report

In this Technical Design Report (TDR) we describe the SuperB detector that was to be installed on the SuperB e+e- high luminosity collider. The SuperB asymmetric collider, which was to be constructed on the Tor Vergata campus near the INFN Frascati National Laboratory, was designed to operate both at the Upsilon(4S) center-of-mass energy with a luminosity of 10^{36} cm^{-2}s^{-1} and at the tau/charm production threshold with a luminosity of 10^{35} cm^{-2}s^{-1}. This high luminosity, producing a data sample about a factor 100 larger than present B Factories, would allow investigation of new physics effects in rare decays, CP Violation and Lepton Flavour Violation. This document details the detector design presented in the Conceptual Design Report (CDR) in 2007. The R&D and engineering studies performed to arrive at the full detector design are described, and an updated cost estimate is presented. A combination of a more realistic cost estimates and the unavailability of funds due of the global economic climate led to a formal cancelation of the project on Nov 27, 2012.

physics.ins-det↗