arXiv subjects

Ch. Cauet

Publications and source records attributed to Ch. Cauet.

At least 37 records · Page 2Linked to original sources

arXiv2013

Measurement of the fraction of \Y1S originating from \chib1P decays in $pp$ collisions at $\sqrt{s} = 7\tev$

The production of \chib1P mesons in $pp$ collisions at a centre-of-mass energy of $7\tev$ is studied using $32\invpb$ of data collected with the \lhcb detector. The $\chib1P$ mesons are reconstructed in the decay mode $\chib1P \to \Y1S\g \to \mumu\g$. The fraction of \Y1S originating from \chib1P decays in the \Y1S transverse momentum range $6 < \pt^{\Y1S} < 15\gevc$ and rapidity range $2.0 < y^{\Y1S} < 4.5$ is measured to be $(20.7\pm 5.7\pm 2.1^{+2.7}_{-5.4})%$, where the first uncertainty is statistical, the second is systematic and the last gives the range of the result due to the unknown \Y1S and \chib1P polarizations.

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arXiv2013

Observation of the decay $B_c^+ \to ψ(2S)π^+$

The decay $B_c^+ \to ψ(2S)π^+$ with $ψ(2S) \to μ^+μ^-$ is observed with a significance of $5.2\,σ$ using $pp$ collision data corresponding to an integrated luminosity of $1.0\,\invfb$ collected by the LHCb experiment. The branching fraction of $B_c^+ \to ψ(2S)π^+$ decays relative to that of the $B_c^+ \to J/ψπ^+$ mode is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+ \to ψ(2S)π^+)}{\mathcal{B}(B_c^+ \to J/ψπ^+)} = 0.250 \pm 0.068 \,\text{stat} \pm 0.014 \,\text{\syst} \pm 0.006 \,(\mathcal{B}). \end{equation*} The last term is the uncertainty on the ratio $\mathcal{B}(ψ(2S) \to μ^+μ^-)/\mathcal{B}(J/ψ\to μ^+μ^-)$.

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arXiv2013

Observations of $B^0_s \rightarrowψ(2S)η$ and $B^0_{(s)}\rightarrowψ(2S)π^+π^-$ decays

First observations of the $B^0_s \rightarrow ψ(2S) η$, $B^0 \rightarrow ψ(2S) π^+ π^-$ and $B^0_s \rightarrow ψ(2S) π^+ π^-$ 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 $ψ(2S)$ modes with respect to the corresponding $J/ψ$ decays are \[ \frac{\mathcal{B}(B^0_s \rightarrow ψ(2S) η) }{\mathcal{B}(B^0_s \rightarrow J/ψη)} =0.83\pm0.14\,(stat)\pm0.12\,(syst)\pm0.02\,(\mathcalB}), \] \[ \frac{\mathcal{B}(B^0 \rightarrow ψ(2S) π^+ π^-)}{\mathcal{B}(B^0 \rightarrow J/ψπ^+ π^-)} =0.56\pm0.07\,(stat)\pm0.05\,(syst)\pm0.01\,(\mathcal{B}), \] \[ \frac{\mathcal{B}(B^0_s \rightarrow ψ(2S) π^+ π^-)}{\mathcal{B}(B^0_s \rightarrow J/ψπ^+ π^-)} =0.34\pm0.04\,(stat)\pm0.03\,(syst)\pm0.01\,(\mathcal{B}), \] where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the $J/ψ$ and $ψ(2S)$ meson decays.

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arXiv2013

Determination of the X(3872) meson quantum numbers

The quantum numbers of the X(3872) meson are determined to be JPC = 1++ based on angular correlations in B+ to X(3872) K+ decays, where X(3872) to pi+pi- J/psi and J/psi to μ+μ-. The data correspond to 1.0 fb-1 of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements, JPC=2-+, is rejected with a confidence level equivalent to more than eight Gaussian standard deviations using the likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.

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arXiv2013

First observations of $\bar{B}_s^0\to D^+D^-$, $D_s^+D^-$ and $D^0\bar{D}^0$ decays

First observations and measurements of the branching fractions of the $\bar{B}_s^0\to D^+D^-$, $\bar{B}_s^0\to D_s^+D^-$ and $\bar{B}_s^0\to D^0\bar{D}^0$ decays are presented using 1.0 fb$^{-1}$ of data collected by the LHCb experiment. These branching fractions are normalized to those of $\bar{B}^0\to D^+D^-$, $B^0\to D_s^+D^-$ and $B^-\to D^0D_s^-$, respectively. An excess of events consistent with the decay $\bar{B}^0\to D^0\bar{D}^0$ is also seen, and its branching fraction is measured relative to that of $B^-\to D^0D_s^-$. Improved measurements of the branching fractions ${\cal{B}}(\bar{B}_s^0\to D_s^+D_s^-)$ and ${\cal{B}}(B^-\to D^0D_s^-)$ are reported, each relative to ${\cal{B}}(B^0\to D_s^+D^-)$. The ratios of branching fractions are {-0.2in} {center} {align*} {\cal{B}(\bar{B}_s^0\to D^+D^-)\over {\cal{B}}(\bar{B}^0\to D^+D^-)} &= 1.08\pm 0.20\pm0.10, {\cal{B}(\bar{B}_s^0\to D_s^+D^-)\over {\cal{B}}(B^0\to D_s^+D^-)} &= 0.050\pm 0.008\pm0.004, {\cal{B}(\bar{B}_s^0\to D^0\bar{D}^0)\over {\cal{B}}(B^-\to D^0D_s^-)} &= 0.019\pm 0.003\pm0.003, {\cal{B}(\bar{B}^0\to D^0\bar{D}^0)\over {\cal{B}}(B^-\to D^0D_s^-)} &= 0.0014\pm 0.0006\pm0.0002,{\cal{B}(\bar{B}_s^0\to D_s^+D_s^-)\over {\cal{B}}(B^0\to D_s^+D^-)} &= 0.56\pm 0.03\pm0.04, {\cal{B}(B^-\to D^0D_s^-)\over {\cal{B}}(B^0\to D_s^+D^-)} &= 1.22\pm 0.02\pm0.07, {align*} {center} \noindent where the uncertainties are statistical and systematic, respectively.

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arXiv2013

Measurement of the CP asymmetry in B0 -> K*0 mu+ mu- decays

A measurement of the CP asymmetry in B0 -> K*0 mu+ mu- decays is presented, based on 1.0fb-1 of pp collision data recorded by the LHCb experiment during 2011. The measurement is performed in six bins of invariant mass squared of the mu+ mu- pair, excluding the J/psi and psi(2S) resonance regions. Production and detection asymmetries are removed using the B0 -> J/Psi K*0 decay as a control mode. The integrated CP asymmetry is found to be -0.072 +- 0.040 (stat.) +- 0.005 (syst.), consistent with the Standard Model.

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arXiv2013

Prompt charm production in pp collisions at sqrt(s)=7 TeV

Charm production at the LHC in pp collisions at sqrt(s)=7 TeV is studied with the LHCb detector. The decays D0 -> K- pi+, D+ -> K- pi+ pi+, D*+ -> D0(K- pi+) pi+, D_s+ -> phi(K- K+) pi+, Lambda_c+ -> p K- pi+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb^{-1}. Differential cross-sections dsigma/dp_T are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0 < p_T < 8 GeV/c and 2.0 < y < 4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above p_T-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives sigma(c\bar{c})_{p_T < 8 GeV/c, 2.0 < y < 4.5} = 1419 +/- 12 (stat) +/- 116 (syst) +/- 65 (frag) microbarn, where the uncertainties are statistical, systematic, and due to the fragmentation functions.

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arXiv2013

Analysis of the resonant components in B0->J/ψpi+pi-

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/ψpi+pi- decays. The final state composition of this channel is investigated using a 1.0/fb sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B0->J/ψpi+pi- branching fraction of (3.97 +/-0.09+/- 0.11 +/- 0.16)x10^{-5} is reported where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainty of the branching fraction of the decay B- -> J/ψK- used as a normalization channel. In the J/ψpi+pi- final state significant production of f0(500) and rho(770) resonances is found, both of which can be used for CP violation studies. In contrast evidence for the f0(980) resonance is not found, thus establishing the first upper limit on the branching fraction product B(B0->J/ψf0(980) x B(f0(980)-> pi+ pi-) < 1.1x10^{-6}, leading to an upper limit on the absolute value of the mixing angle of the f0(980)$ with the f0(500) of <31 degrees, both at 90% confidence level.

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arXiv2013

Measurement of the Λ_b^0, Ξ_b^- and Ω_b^- baryon masses

Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0 fb^{-1} of data collected in 2011 with the LHCb detector. Significant Λ_b^0 \rightarrow J/ψΛ, Ξ_b^-\rightarrow J/ψΞ^- and Ω_b^- \rightarrow J/ψΩ^- signals are observed and the corresponding masses are measured to be M(Λ_b^0) = 5619.53 \pm 0.13 (stat) \pm 0.45 (syst) MeV/c^2, M(Ξ_b^-) = 5795.8 \pm 0.9 (stat) \pm 0.4 (syst) MeV/c^2, M(Ω_b^-) = 6046.0 \pm 2.2 (stat) \pm 0.5 (syst) MeV/c^2, while the differences with respect to the Λ_b^0 mass are M(Ξ_b^-)-M(Λ_b^0) = 176.2 \pm 0.9 (stat) \pm 0.1 (syst) MeV/c^2, M(Ω_b^-)-M(Λ_b^0) = 426.4 \pm 2.2 (stat) \pm 0.4 (syst) MeV/c^2. These are the most precise mass measurements of the Λ_b^0, Ξ_b^- and Ω_b^- baryons to date. Averaging the above Λ_b^0 mass measurement with that published by LHCb using 35 pb^{-1} of data collected in 2010 yields M(Λ_b^0) = 5619.44 \pm 0.13 (stat) \pm 0.38 (syst) MeV/c^2.

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arXiv2013

Exclusive $J/ψ$ and $ψ(2S)$ production in $pp$ collisions at $\sqrt{s}=7$ TeV

Exclusive $J/ψ$ and $ψ(2S)$ vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between 2.0 and 4.5 are measured to be $ σ_{pp\rightarrow J/ψ(\rightarrow μ^{+} μ^{-})} (2.0 <η_{μ^{\pm}}< 4.5) = 307 \pm 21 \pm 36 \text{pb}, σ_{pp\rightarrow ψ(2S) (\rightarrow μ^{+} μ^{-})} (2.0 <η_{μ^{\pm}}< 4.5) = 7.8 \pm 1.3 \pm 1.0 \text{pb}, $ where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The $J/ψ$ photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.

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arXiv2013

Search for the rare decay KS -> mu+ mu-

A search for the decay KS -> mu+ mu- is performed, based on a data sample of 1.0 fb^-1 of pp collisions at \sqrt{s}=7 TeV collected by the LHCb experiment at the Large Hadron Collider. The observed number of candidates is consistent with the background-only hypothesis, yielding an upper limit of BR(KS -> mu+ mu-) < 11 (9) x 10^-9 at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement.

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arXiv2013

First observation of the decay $B^{+} \rightarrow π^{+} μ^{+} μ^{-}$

A discovery of the rare decay $B^{+} \rightarrow π^{+} μ^{+} μ^{-}$ is presented. This decay is observed for the first time, with 5.2 $σ$ significance. The observation is made using $pp$ collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector. The measured branching fraction is (2.3 $\pm$ 0.6 (stat.) $\pm$ 0.1 (syst.))$\times 10^{-8}$, and the ratio of the $B^{+} \rightarrow π^{+} μ^{+} μ^{-}$ and $B^{+} \rightarrow \K^{+} μ^{+} μ^{-}$ branching fractions is measured to be 0.053 $\pm$ 0.014 (stat.) $\pm$ 0.001 (syst.).

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arXiv2013

First evidence for the annihilation decay mode $B^{+} \to D_{s}^{+} ϕ$

Evidence for the hadronic annihilation decay mode $B^{+} \to D_s^{+}ϕ$ is found with greater than $3σ$ significance. The branching fraction and \CP asymmetry are measured to be \mathcal{B}(B^{+} \to D_s^{+}ϕ) &=& (1.87^{+1.25}_{-0.73}({\rm stat}) \pm 0.19 ({\rm syst}) \pm 0.32 ({\rm norm})) \times 10^{-6}, \mathcal{A}_{CP}(B^{+} \to D_s^{+}ϕ) &=& -0.01 \pm 0.41 ({\rm stat}) \pm 0.03 ({\rm syst}). The last uncertainty on $\mathcal{B}(B^{+} \to D_s^{+}ϕ)$ is from the branching fractions of the $B^+ \to D_s^+ \kern 0.2em\bar{\kern -0.2em D}{}^0$ normalization mode and intermediate resonance decays. Upper limits are also set for the branching fractions of the related decay modes $B^{+}_{(c)} \to D^{+}_{(s)} K^{*0}$, $B^{+}_{(c)} \to D^{+}_{(s)} \kern 0.2em\bar{\kern -0.2em K}{}^{*0}$ and ${B_c^{+} \to D^{+}_{s}ϕ}$, including the result ${\mathcal{B}(B^+ \to D^+ K^{*0})} < 1.8 \times 10^{-6}$ at the 90% credibility level.

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arXiv2012

First observation of the decays $\bar{B}^0_{(s)}\to D_s^+K^-π^+π^-$ and $\bar{B}^0_s\to D_{s1}(2536)^+π^-$

The first observation of the decays $\bar{B}^0_{s}\to D_s^+K^-π^+π^-$ and $\bar{B}^0\to D_s^+K^-π^+π^-$ are reported using an integrated luminosity of 1.0 fb$^{-1}$ recorded by the LHCb experiment. The branching fractions, normalized with respect to $\bar{B}^0_{s}\to D_s^+π^-π^+π^-$ and $\bar{B}^0_{s}\to D_s^+K^-π^+π^-$, respectively, are measured to be {\br(\bar{B}^0_{s}\to D_s^+K^-π^+π^-)\over\br(\bar{B}^0_{s}\to D_s^+π^-π^+π^-)} &= (5.2\pm0.5\pm0.3)\times10^{-2}, {\br(\bar{B}^0\to D_s^+K^-π^+π^-)\over\br(\bar{B}^0_{s}\to D_s^+K^-^π^+π^-)} &= 0.54\pm0.07\pm0.07, where the first uncertainty is statistical and the second is systematic. The $\bar{B}^0_{s}\to D_s^+K^-π^+π^-$ decay is of particular interest as it can be used to measure the weak phase $γ$. First observation of the $\bar{B}^0_s\to D_{s1}(2536)^+π^-, D_{s1}^+\to D_s^+π^-π^+$ decay is also presented, and its branching fraction relative to $\bar{B}^0_{s}\to D_s^+π^-π^+π^-$ is found to be {\br(\bar{B}^0_s\to D_{s1}(2536)^+π^-, D_{s1}^+\to D_s^+π^-π^+)\over\br(\bar{B}^0_{s}\to D_s^+π^-π^+π^-)} &= (4.0\pm1.0\pm0.4)\times10^{-3}.

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arXiv2012

Measurement of the D+/- production asymmetry in 7 TeV pp collisions

The asymmetry in the production cross-section σof D+/- mesons, A_P = (σ(D+) - σ(D-))/(σ(D+) + σ(D-)), is measured in bins of pseudorapidity ηand transverse momentum p_T within the acceptance of the LHCb detector. The result is obtained with a sample of D+ -> K_S pi+ decays corresponding to an integrated luminosity of 1.0 fb^-1, collected in pp collisions at a centre of mass energy of 7 TeV at the Large Hadron Collider. When integrated over the kinematic range 2.0 < p_T < 18.0 GeV/c and 2.20 < η< 4.75, the production asymmetry is A_P = (-0.96+/-0.26+/-0.18)%. The uncertainties quoted are statistical and systematic, respectively. The result assumes that any direct CP violation in the D+ -> K_S pi+ decay is negligible. No significant dependence on ηor p_T is observed.

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arXiv2012

Measurement of the cross-section ratio $σ(χ_{c2})/σ(χ_{c1})$ for prompt $χ_c$ production at $\sqrt{s}=7$ TeV

The prompt production of the charmonium $χ_{c1}$ and $χ_{c2}$ mesons has been studied in proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The $χ_c$ mesons are identified through their decays $χ_c\to J/ψ\,γ$ with $J/ψ\to μ^+ μ^-$ using 36 $\mathrm{pb^{-1}}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for the two $χ_c$ spin states, $σ(χ_{c2})/σ(χ_{c1})$, has been determined as a function of the $J/ψ$ transverse momentum, $p_{\mathrm{T}}^{J/ψ}$, in the range from 2 to 15 GeV/$c$. The results are in agreement with the next-to-leading order non-relativistic QCD model at high $p_{\mathrm{T}}^{J/ψ}$ and lie consistently above the pure leading-order colour singlet prediction.

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arXiv2012

Measurement of the ratio of prompt $χ_{c}$ to $J/ψ$ production in $pp$ collisions at $\sqrt{s}=7$ TeV

The prompt production of charmonium $χ_{c}$ and $J/ψ$ states is studied in proton-proton collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the Large Hadron Collider. The $χ_{c}$ and $J/ψ$ mesons are identified through their decays $χ_{c}\rightarrow J/ψγ$ and $J/ψ\rightarrow μ^+μ^-$ using 36 pb$^{-1}$ of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for $χ_{c}$ and $J/ψ$, $σ(χ_{c}\rightarrow J/ψγ)/ σ(J/ψ)$, is determined as a function of the $J/ψ$ transverse momentum in the range $2 < p_{\mathrm T}^{J/ψ} < 15$ GeV/$c$. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low $p_{\mathrm T}^{J/ψ}$ region.

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arXiv2012

Observation of excited Lambda_b0 baryons

Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda_b0pi+pi- spectrum with masses 5911.97 +- 0.12(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.77 +- 0.08(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).

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