PH-EP Articles

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2013-05-17
11:55
 Study of $B^{0} \rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+}$ and $B^{0} \rightarrow D^{*-}K^{+}\pi^{-}\pi^{+}$ decays / LHCb Collaboration Using proton-proton collision data collected by the LHCb experiment at $\sqrt{s} =$ 7 TeV, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, the ratio of branching fractions of the $B^{0}\rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+}$ decay relative to the $B^{0} \rightarrow D^{*-}\pi^{+}$ decay is measured to be \begin{equation*} \frac{\mathcal{B}(B^{0}\rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+})}{\mathcal{B}(B^{0} \rightarrow D^{*-}\pi^{+})} = 2.64 \pm 0.04\,(\text{stat.}) \pm 0.13\,(\text{syst.})\, . \label{eq:CF_BF_ratio_result} \end{equation*} The Cabibbo-suppressed decay $B^{0}\rightarrow D^{*-}K^{+}\pi^{-}\pi^{+}$ is observed for the first time and the measured ratio of branching fractions is \begin{equation*} \frac{\mathcal{B}(B^{0}\rightarrow D^{*-}K^{+}\pi^{-}\pi^{+})}{\mathcal{B}(B^{0} \rightarrow D^{*-}\pi^{+}\pi^{-}\pi^{+})} = (6.47 \pm 0.37\,(\text{stat.}) \pm 0.35\,(\text{syst.})) \times 10^{-2} \label{eq:CS_BF_ratio_result}\, . [...] arXiv:1303.6861; LHCB-PAPER-2012-046; CERN-PH-EP-2013-041.- Geneva : CERN, 2013 - 17 p. - Published in : Phys. Rev. D 87 (2013) 092001 APS Open Access article: PDF; Related data file(s): ZIP; External link: Preprint

2013-04-17
17:41
 Measurement of the effective $B_s^0\rightarrow J/\psi K_{\mathrm S}^0$ lifetime / LHCb Collaboration This paper reports the first measurement of the effective $B_s^0\rightarrow J/\psi K_{\mathrm S}^0$ lifetime and an updated measurement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of $1.0\:\text{fb}^{-1}$ of $pp$ collisions, recorded by the LHCb experiment in 2011 at a centre-of-mass energy of $7\:\text{TeV}$. [...] arXiv:1304.4500; CERN-PH-EP-2013-063; LHCB-PAPER-2013-015.- Geneva : CERN, 2013 - 20 p. - Published in : Nucl. Phys. B 873 (2013) 275-292 Elsevier Open Access article: PDF; Fulltext: PDF; Related data file(s): ZIP; External link: Preprint

2013-03-08
17:11
 Observation of the decay $B_c^+ \to \psi(2S)\pi^+$ / LHCb Collaboration The decay $B_c^+ \to \psi(2S)\pi^+$ with $\psi(2S) \to \mu^+\mu^-$ is observed with a significance of $5.2\,\sigma$ using $pp$ collision data corresponding to an integrated luminosity of 1.0 $fb^{-1}$ collected by the LHCb experiment. The branching fraction of $B_c^+ \to \psi(2S)\pi^+$ decays relative to that of the $B_c^+ \to J/\psi\pi^+$ mode is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+ \to \psi(2S)\pi^+)}{\mathcal{B}(B_c^+ \to J/\psi\pi^+)} = 0.250 \pm 0.068 \,\text{stat} \pm 0.014 \,\text{\syst} \pm 0.006 \,(\mathcal{B}). [...] arXiv:1303.1737; LHCB-PAPER-2012-054; CERN-PH-EP-2013-028.- Geneva : CERN, 2013 - 12 p. - Published in : Phys. Rev. D 87 (2013) 071103 APS Open Access article: PDF; Related data file(s): ZIP; External link: Preprint

2013-02-27
11:54
 Observation of the $B^0_{s}\to\psi{(2\mathrm{S})}\eta$ and $B^0_{(s)}\to\psi{(2\mathrm{S})}\pi^+\pi^-$ decays / LHCb Collaboration First observations of the $B^0_s \rightarrow \psi(2S) \eta$, $B^0 \rightarrow \psi(2S) \pi^+ \pi^-$ and $B^0_s \rightarrow \psi(2S) \pi^+ \pi^-$ decays are made using a dataset corresponding to an integrated luminosity of 1.0 $fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The ratios of the branching fractions of each of the $\psi(2S)$ modes with respect to the corresponding $J/\psi$ decays are $\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta) }{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} =0.83\pm0.14\,(stat)\pm0.12\,(syst)\pm0.02\,(\mathcal{B}),$ $\frac{\mathcal{B}(B^0 \rightarrow \psi(2S) \pi^+ \pi^-)}{\mathcal{B}(B^0 \rightarrow J/\psi \pi^+ \pi^-)} =0.56\pm0.07\,(stat)\pm0.05\,(syst)\pm0.01\,(\mathcal{B}),$ $\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \pi^+ \pi^-)}{\mathcal{B}(B^0_s \rightarrow J/\psi \pi^+ \pi^-)} =0.34\pm0.04\,(stat)\pm0.03\,(syst)\pm0.01\,(\mathcal{B}),$ where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the $J/\psi$ and $\psi$(2S) meson decays.. arXiv:1302.6354; CERN-PH-EP-2013-024; LHCB-PAPER-2012-053.- Geneva : CERN, 2013 - 16 p. - Published in : Nucl. Phys. B 871 (2013) 403-419 Elsevier Open Access article: PDF; Related data file(s): ZIP; External link: Preprint

2013-02-11
19:15
 Study of the underlying event at forward rapidity in pp collisions at $\sqrt{s}$ = 0.9, 2.76, and 7 TeV / CMS Collaboration The underlying event activity in proton-proton collisions at forward pseudorapidity (-6.6 $\lt \eta \lt$ -5.2) is studied with the CMS detector at the LHC, using a novel observable: the ratio of the forward energy density, dE/d$\eta$, for events with a charged-particle jet produced at central pseudorapidity (abs(eta[jet]) $\lt$ 2) to the forward energy density for inclusive events. This forward energy density ratio is measured as a function of the central jet transverse momentum, pt, at three different pp centre-of-mass energies ($\sqrt{s}$ = 0.9, 2.76, and 7 TeV). [...] arXiv:1302.2394; CMS-FWD-11-003; CERN-PH-EP-2013-012.- Geneva : CERN, 2013 - 33 p. - Published in : J. High Energy Phys. 04 (2013) 072 Springer Open Access article: PDF; External link: Preprint

2013-01-30
16:51
 A Particle Consistent with the Higgs Boson Observed with the ATLAS Detector at the Large Hadron Collider / ATLAS Collaboration Nearly 50 years ago, theoretical physicists proposed that a field permeates the universe and gives energy to the vacuum. This field was required to explain why some, but not all, fundamental particles have mass. [...] CERN-PH-EP-2012-303.- Geneva : CERN, 2012 - 8 p. - Published in : Science 338 (2012) 1576-1582 Fulltext: PDF PDF (PDFA); External links: Previous draft version; Supplementary Materials

2013-01-25
14:22
 Measurement of the $t\bar{t}$ production cross section in the $\tau$+jets channel in pp collisions at $\sqrt{s}$ = 7 TeV / CMS Collaboration The top-quark pair production cross section in 7 TeV centre-of-mass proton proton collisions is measured using data collected by the CMS detector at the LHC. The measurement uses events with one jet identified as a hadronically-decaying tau lepton and at least four additional energetic jets, at least one of which is identified as coming from a b quark. [...] arXiv:1301.5755; CMS-TOP-11-004; CERN-PH-EP-2012-374.- Geneva : CERN, 2013 - 27 p. - Published in : Eur. Phys. J. C 73 (2013) 2386 Springer Open Access article: PDF; External link: Preprint

2013-01-25
13:31
 Analysis of the resonant components in $\overline{B}^0 \to J/\psi \pi^+ \pi^-$ / LHCb collaboration Interpretation of CP violation measurements using charmonium decays, in both the B0 and Bs systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using measurements of the Cabibbo-suppressed B0->J/\psi pi+pi- decays. [...] arXiv:1301.5347; LHCB-PAPER-2012-045; CERN-PH-EP-2013-004.- Geneva : CERN, 2013 - 38 p. - Published in : Phys. Rev. D 87 (2013) 052001 APS Open Access article: PDF; Related data file(s): ZIP; External link: Preprint

2013-01-20
23:18
 Measurement of $W^+W^-$ and ZZ production cross sections in pp collisions at $\sqrt{s}$=8 TeV / CMS Collaboration The W+W- and ZZ production cross sections are measured in proton-proton collisions at $\sqrt{s}$ = 8 TeV with the CMS experiment at the LHC in data samples corresponding to an integrated luminosity of up to 5.3 inverse femtobarns. The measurements are performed in the leptonic decay modes W+W- to l' nu l' nu and ZZ to 2l 2l', where l = e, mu and l' = e, mu, tau. [...] arXiv:1301.4698; CMS-SMP-12-024; CERN-PH-EP-2012-376.- Geneva : CERN, 2013 - Published in : Phys. Lett. B 721 (2013) 190-211 Elsevier Open Access article: PDF; External link: Preprint

2012-12-30
15:58
 Measurement of the $t\bar{t}$ production cross section in pp collisions at $\sqrt{s}$ = 7 TeV with lepton + jets final states / CMS Collaboration A measurement of the t t-bar production cross section in pp collisions at $\sqrt{s}$ = 7 TeV is presented. The results are based on data corresponding to an integrated luminosity of 2.3 inverse femtobarns collected by the CMS detector at the LHC. [...] arXiv:1212.6682; CMS-TOP-11-003; CERN-PH-EP-2012-285.- Geneva : CERN, 2013 - 31 p. - Published in : Phys. Lett. B 720 (2013) 83-104 Elsevier Open access article: PDF; External link: Preprint