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.
A search for the rare two-body charmless baryonic decay B + → p$-\atop{Λ}$ is performed with pp collision data, corresponding to an integrated luminosity of 3 fb-1, collected by the LHCb experiment ...at centre-of-mass energies of 7 and 8 TeV. An excess of B + →p$-\atop{Λ}$ candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the B + →K S 0 π + decay for normalisation, B(B+→p$-\atop{Λ}$=2.4$+1.0\atop{0.8}$±0.3 x 10-7)where the first uncertainty is statistical and the second systematic.
A measurement of the effective Bs0→K+K− lifetime is presented using approximately 37 pb−1 of data collected by LHCb during 2010. This quantity can be used to put constraints on contributions from ...processes beyond the Standard Model in the Bs0 meson system and is determined by two complementary approaches asτKK=1.440±0.096 (stat)±0.008 (syst)±0.003 (model) ps.
A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D0→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⁎+→D0π+ and D⁎−→D‾0π− decays. The time-integrated CP asymmetry ACP(K−K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D0→K−π+, D+→K−π+π+ and D+→K‾0π+ decays used as calibration channels. It is found to beACP(K−K+)=(0.14±0.15 (stat)±0.10 (syst))%. A combination of this result with previous LHCb measurements yieldsACP(K−K+)=(0.04±0.12 (stat)±0.10 (syst))%,ACP(π−π+)=(0.07±0.14 (stat)±0.11 (syst))%. These are the most precise measurements from a single experiment. The result for ACP(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.
An amplitude analysis of the decay $Λ_b^0$ → $D^0pπ^-$ is performed in the part of the phase space containing resonances in the $D^0p$ channel. The study is based on a data sample corresponding to an ...integrated luminosity of 3.0 fb-1 of $pp$ collisions recorded by the LHCb experiment. The spectrum of excited $Λ^+_c$ states that decay into $D^0p$ is studied. The masses, widths and quantum numbers of the $Λ_c$(2880)+ and $Λ_c$(2940)+ resonances are measured. The constraints on the spin and parity for the $Λ_c$(2940)+ state are obtained for the first time. A near-threshold enhancement in the $D^0p$ amplitude is investigated and found to be consistent with a new resonance, denoted the $Λ_c$(2860)+, of spin 3/2 and positive parity.
The first full amplitude analysis of B+ → J/ψϕK+ with J/ψ → μ+μ-, ϕ → K+K- decays is performed with a data sample of 3 fb-1 of pp collision data collected at $\sqrt{s}$ =7 and ...8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK+, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The associated production of a Z boson or an off-shell photon gamma super( )*with a bottom quark in the forward region is ...studied using proton-proton collisions at a centre-of-mass energy of 7 TeV. The Z bosons are reconstructed in the Z/ gamma super( )* arrow right mu super( )+ mu super( )-final state from muons with a transverse momentum larger than 20 GeV, while two transverse momentum thresholds are considered for jets (10 GeV and 20 GeV). Both muons and jets are reconstructed in the pseudorapidity range 2.0 < eta < 4.5. The results are based on data corresponding to 1.0 fb super(-1) recorded in 2011 with the LHCb detector. The measurement of the Z+b-jet cross-section is normalized to the Z+jet cross-section. The measured cross-sections are ... ... for p sub(T)(jet) > 10 GeV, and ... ... for p sub(T)(jet) > 20 GeV. Figure not available: see fulltext.
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