The production of J/ψ pairs in proton–proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb−1 collected with the LHCb detector. The ...production cross-section for pairs with both J/ψ in the rapidity range 2<yJ/ψ<4.5 and transverse momentum pTJ/ψ<10 GeV/c isσJ/ψJ/ψ=5.1±1.0±1.1 nb, where the first uncertainty is statistical and the second systematic.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted) Measurements of b hadron production ratios in proton-proton collisions at a center-of-mass energy of 7 TeV with an integrated ...luminosity of 3 pb super(-1) are presented. We study the ratios of strange B meson to light B meson production functionof sub(s)/(functionof sub(u) + functionof sub(d)) and ... baryon to light B meson production functionof sub(Lambda)b/(functionof sub(u) + functionof sub(d)) as a function of the charmed hadron-muon pair transverse momentum p sub(T) and the b hadron pseudorapidity eta, for p sub(T) between 0 and 14 GeV and eta between 2 and 5. We find that functionof sub(s)/(functionof sub(u) + functionof sub(d)) is consistent with being independent of p sub(T) and eta, and we determine ..., where the first error is statistical and the second systematic. The corresponding ratio functionof sub(Lambda)b/(functionof sub(u) + functionof sub(d)) is found to be dependent upon the transverse momentum of the charmed hadron-muon pair, functionof sub(Lambda)b/(functionof sub(u) + functionof sub(d)) = (0.404 + or - 0.017(stat) + or - 0.027(syst) + or - 0.105(Br)), where Br reflects an absolute scale uncertainty due to the poorly x 1 - (0.031 + or - 0.004(stat) + or - 0.003(syst)) x p sub(T)(GeV) known branching fraction ... We extract the ratio of strange B meson to light neutral B meson production functionof sub(s)/functionof sub(d) by averaging the result eported here with two previous measurements derived from the relative abundances of ... to B super(0 arrow right )D super(+)K super(-) and B super(0) arrow right a D super(+)pi super(-). We obtain ...
The angular distribution and differential branching fraction of the decay $B^{0} \to K^{*0} \mu^{+}\mu^{-}$ are studied using a data sample, collected by the LHCb experiment in $pp$ collisions at ...$\sqrt{s}=7\,{\rm TeV}$, corresponding to an integrated luminosity of $1.0\,{\rm fb}^{-1}$. Several angular observables are measured in bins of the dimuon invariant mass squared, $q^{2}$. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be $q_{0}^{2} = 4.9 \pm 0.9 \,{\rm GeV}^{2}/c^{4}$, where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions.
Here, the decay B0→ψ(2S)K+π- is analyzed using 3 fb-1 of pp collision data collected with the LHCb detector. A model-independent description of the ψ(2S)π mass spectrum is obtained, using as input ...the Kπ mass spectrum and angular distribution derived directly from data, without requiring a theoretical description of resonance shapes or their interference. The hypothesis that the ψ(2S)π mass spectrum can be described in terms of Kπ reflections alone is rejected with more than 8σ significance. This provides confirmation, in a model-independent way, of the need for an additional resonant component in the mass region of the Z(4430)- exotic state.
A
bstract
A study is presented of central exclusive production of Υ(
nS
) states, where the Υ(
nS
) resonances decay to the
μ
+
μ
−
final state, using
pp
collision data recorded by the LHCb ...experiment. The cross-section is measured in the rapidity range 2
< y
(Υ)
<
4
.
5 where the muons are reconstructed in the pseudorapidity range 2
< η
(
μ
±
)
<
4
.
5. The data sample corresponds to an integrated luminosity of 2.9 fb
−1
and was collected at centre-of-mass energies of 7 TeV and 8 TeV. The measured Υ(1
S
) and Υ(2
S
) production cross-sections are
σ
pp
→
p
Υ
1
S
p
=
9.0
±
2.1
±
1.7
p
b
and
σ
pp
→
p
Υ
2
S
p
=
1.3
±
0.8
±
0.3
p
b
,
where the first uncertainties are statistical and the second are systematic. The Υ(1
S
) crosssection is also measured as a function of rapidity and is found to be in good agreement with Standard Model predictions. An upper limit is set at 3.4 pb at the 95% confidence level for the exclusive Υ(3
S
) production cross-section, including possible contamination from χ
b
(3
P
) → Υ(3
S
)γ decays.
Two structures are observed close to the kinematic threshold in the Ξ 0 b π − mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb − 1 , ...recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content b d s are expected in this mass region: the spin-parity J P = ( 1 / 2 ) + and J P = ( 3 / 2 ) + states, denoted Ξ ' − b and Ξ * − b . Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be m ( Ξ ' − b ) − m ( Ξ 0 b ) − m ( π − ) = 3.653 ± 0.018 ± 0.006 MeV / c 2 , m ( Ξ * − b ) − m ( Ξ 0 b ) − m ( π − ) = 23.96 ± 0.12 ± 0.06 MeV / c 2 , Γ ( Ξ * − b ) = 1.65 ± 0.31 ± 0.10 MeV , where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of Γ ( Ξ ' − b ) < 0.08 MeV at 95% confidence level. Relative production rates of these states are also reported.
A
bstract
Associated production of bottomonia and open charm hadrons in pp collisions at
s
=
7
and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb
−1
accumulated with ...the LHCb detector. The observation of five combinations, Y(1S)D
0
, Y(2S)D
0
, Y(1S)D
+
, Y(2S)D
+
and Y(1S)D
s
+
, is reported. Production crosssections are measured for Y(1S)D
0
and Y(1S)D
+
pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism.
A search is presented for hidden-sector bosons, $\chi$, produced in the decay ${B^0\!\to K^*(892)^0\chi}$, with $K^*(892)^0\!\to K^{+}\pi^{-}$ and $\chi\!\to\mu^+\mu^-$. The search is performed using ...$pp$-collision data corresponding to 3.0 fb$^{-1}$ collected with the LHCb detector. No significant signal is observed in the accessible mass range $214 \leq m({\chi}) \leq 4350$ MeV, and upper limits are placed on the branching fraction product $\mathcal{B}(B^0\!\to K^*(892)^0\chi)\times\mathcal{B}(\chi\!\to\mu^+\mu^-)$ as a function of the mass and lifetime of the $\chi$ boson. These limits are of the order of $10^{-9}$ for $\chi$ lifetimes less than 100 ps over most of the $m(\chi)$ range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.
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 5911.95 +- ...0.12(stat) +- 0.03(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.76 +- 0.07(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 4.9 and 10.1 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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