0000000000285083
AUTHOR
M. Borsato
Precision measurement of the ratio of the Λb0 to B¯0 lifetimes
The LHCb measurement of the lifetime ratio of the Lambda(0)(b) baryon to the (B) over bar (0) meson is updated using data corresponding to an integrated luminosity of 3.0 fb(-1) collected using 7 and 8 TeV centre-of-mass energy pp collisions at the LHC. The decay modes used are Lambda(0)(b) -> J/psi pK(-) and (B) over bar (0) -> J/psi pi K-+(-), where the pi K-+(-) mass is consistent with that of the (K) over bar*(0)(892) meson. The lifetime ratio is determined with unprecedented precision to be 0.974 +/- 0.006 +/- 0.004, where the first uncertainty is statistical and the second systematic. This result is in agreement with original theoretical predictions based on the heavy quark expansion.…
First Observation of Top Quark Production in the Forward Region
Top quark production in the forward region in proton-proton collisions is observed for the first time. The W + b final state with W → μν is reconstructed using muons with a transverse momentum, p[subscript T], larger than 25 GeV in the pseudorapidity range 2.0 20 GeV. The results are based on data corresponding to integrated luminosities of 1.0 and 2.0 fb[superscript -1] collected at center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross sections in the fiducial region are σ(top)[7 TeV] = 239 ± 53(stat) ± 33(syst) ± 24(theory) fb, σ(top)[8 TeV] = 289 ± 43(stat) ± 40(syst) ± 29(theory) fb.These results, along with the observed differential yields and c…
Study of W Boson Production in Association with Beauty and Charm
The associated production of a W boson with a jet originating from either a light parton or heavy-flavor quark is studied in the forward region using proton-proton collisions. The analysis uses data corresponding to integrated luminosities of 1.0 and 2.0 fb[superscript -1] collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, respectively. The W bosons are reconstructed using the W → μν decay and muons with a transverse momentum, p[subscript T], larger than 20 GeV in the pseudorapidity range 2.0 20 GeV and 2.2 20 GeV. The fraction of W + jet events that originate from beauty and charm quarks is measured, along with the charge asymmetries of the W + b and W + c produ…
Measurement of the chi(b) (3 P) mass and of the relative rate of chi(b1) (1 P) and chi(b2) (1 P) production
The production of $\chi_b$ mesons in proton-proton collisions is studied using a data sample collected by the LHCb detector, at centre-of-mass energies of $\sqrt{s}=7$ and $8$ TeV and corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $\chi_b$ mesons are identified through their decays to $\Upsilon(1S)\gamma$ and $\Upsilon(2S)\gamma$ using photons that converted to $e^+e^-$ pairs in the detector. The $\chi_b(3P)$ meson mass, and the relative prompt production rate of $\chi_{b1}(1P)$ and $\chi_{b2}(1P)$ mesons as a function of the $\Upsilon(1S)$ transverse momentum in the $\chi_b$ rapidity range 2.0< $y$<4.5, are measured. Assuming a mass splitting between the $\chi_{b1}(3P)$ an…
Observation of charmonium pairs produced exclusively in $pp$ collisions
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{-1}$ collected at centre-of-mass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(-3.5,-1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measu…
Measurement of CP asymmetry in D 0 → K - K + and D 0 → π - πdecays
Time-integrated $CP$ asymmetries in $D^0$ decays to the final states $K^- K^+$ and $\pi^- \pi^+$ are measured using proton-proton collisions corresponding to $3\mathrm{\,fb}^{-1}$ of integrated luminosity collected at centre-of-mass energies of $7\mathrm{\,Te\kern -0.1em V}$ and $8\mathrm{\,Te\kern -0.1em V}$. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in $CP$ asymmetries between the two final states is measured to be \begin{align} \Delta A_{CP} = A_{CP}(K^-K^+)-A_{CP}(\pi^-\pi^+) = (+0.14 \pm 0.16\mathrm{\,(stat)} \pm 0.08\mathrm{\,(syst)})\% \ . \nonu…
Measurement of CP asymmetry in Bs0 → Ds ∓K± decays
Journal of high energy physics 2018(3), 59 (2018). doi:10.1007/JHEP03(2018)059
Measurement of the mass and lifetime of the Ω(−)(b) baryon
A proton-proton collision data sample, corresponding to an integrated luminosity of 3 fb$^{-1}$ collected by LHCb at $\sqrt{s}=7$ and 8 TeV, is used to reconstruct $63\pm9$ $\Omega_b^-\to\Omega_c^0\pi^-$, $\Omega_c^0\to pK^-K^-\pi^+$ decays. Using the $\Xi_b^-\to\Xi_c^0\pi^-$, $\Xi_c^0\to pK^-K^-\pi^+$ decay mode for calibration, the lifetime ratio and absolute lifetime of the $\Omega_b^-$ baryon are measured to be \begin{align*} \frac{\tau_{\Omega_b^-}}{\tau_{\Xi_b^-}} &= 1.11\pm0.16\pm0.03, \\ \tau_{\Omega_b^-} &= 1.78\pm0.26\pm0.05\pm0.06~{\rm ps}, \end{align*} where the uncertainties are statistical, systematic and from the calibration mode (for $\tau_{\Omega_b^-}$ only). A measurement …
Observation of $Z$ production in proton-lead collisions at LHCb
The first observation of $Z$ boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of $\sqrt{s_{NN}}=5~\text{TeV}$ is presented. The data sample corresponds to an integrated luminosity of $1.6~\text{nb}^{-1}$ collected with the LHCb detector. The $Z$ candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above $20~\text{GeV}/c$. The invariant dimuon mass is restricted to the range $60-120~\text{GeV}/c^2$. The $Z$ production cross-section is measured to be \begin{eqnarray*} ��_{Z\to��^+��^-}(\text{fwd})&=&13.5^{+5.4}_{-4.0}\text{(stat.)}\pm1.2\text{(syst.)}~\text{nb} …
Differential branching fractions and isospin asymmetries of B -> K ((*)) μ(+) μ(-) decays
The isospin asymmetries of $B \to K\mu^+\mu^-$ and $B \to K^{*}\mu^+\mu^-$ decays and the partial branching fractions of the $B^0 \to K^0\mu^+\mu^-$, $B^+ \to K^+\mu^+\mu^-$ and $B^+ \to K^{*+}\mu^+\mu^-$ decays are measured as functions of the dimuon mass squared, $q^2$. The data used correspond to an integrated luminosity of 3$~$fb$^{-1}$ from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7$\,$TeV and 8$\,$TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions, while individually consistent, all favour lower values than their respective Standard M…
Measurement of CP asymmetries in the decays B0 → K*0 μ+μ- and B+ → K+ μ+μ-
The direct CP asymmetries of the decays B 0 → K *0 μ + μ − and B + → K + μ + μ − are measured using pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected with the LHCb detector. The respective control modes B 0 → J/ψK *0 and B + → J/ψK + are used to account for detection and production asymmetries. The measurements are made in several intervals of μ + μ − invariant mass squared, with the ϕ(1020) and charmonium resonance regions excluded. Under the hypothesis of zero CP asymmetry in the control modes, the average values of the asymmetries are ACP(B0→K∗0μ+μ−)=−0.035±0.024±0.003,ACP(B+→K+μ+μ−)=0.012±0.017±0.001, where the first uncertainties are statistical and the …
Search for CP violation using T-odd correlations in D-0 -> K+K-pi(+)pi(-) decays
A search for $CP$ violation using $T$-odd correlations is performed using the four-body $D^0 \to K^+K^-\pi^+\pi^-$ decay, selected from semileptonic $B$ decays. The data sample corresponds to integrated luminosities of $1.0\,\text{fb}^{-1}$ and $2.0\,\text{fb}^{-1}$ recorded at the centre-of-mass energies of 7 TeV and 8 TeV, respectively. The $CP$-violating asymmetry $a_{CP}^{T\text{-odd}}$ is measured to be $(0.18\pm 0.29\text{(stat)}\pm 0.04\text{(syst)})\%$. Searches for $CP$ violation in different regions of phase space of the four-body decay, and as a function of the $D^0$ decay time, are also presented. No significant deviation from the $CP$ conservation hypothesis is found.
First study of the CP-violating phase and decay-width difference in Bs0→ψ(2S)ϕ decays
A time-dependent angular analysis of Bs0→ψ(2S)ϕ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0fb−1 collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the Bs0 system are measured to be ϕs=0.23−0.28+0.29±0.02rad and ΔΓs=0.066−0.044+0.041±0.007ps−1, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the ψ(2S) resonance.
Observation of Two NewΞb−Baryon Resonances
Two structures are observed close to the kinematic threshold in the Ξb0π- mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb-1, recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content bds are expected in this mass region: the spin-parity JP=(1/2)+ and JP=(3/2)+ states, denoted Ξb′- and Ξb∗-. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m(Ξb′-)-m(Ξb0)-m(π-)=3.653±0.018±0.006MeV/c2, m(Ξb∗-)-m(Ξb0)-m(π-)=23.96±0.12±0.06MeV/c2, Γ(Ξb∗-)=1.65±0.31±0.10MeV, where the first and second uncertainties are statistical and systema…
AGATA-Advanced GAmma Tracking Array
WOS: 000300864200005