A
bstract
Evidence for the hadronic annihilation decay mode
$ {B^{+}}\to D_s^{+}\phi $
is found with greater than 3
σ
significance. The branching fraction and
CP
asymmetry are measured to be
$ ...\begin{array}{*{20}{c}} {\quad\;\mathcal{B}\left( {{B^{+}}\to D_s^{+}\phi } \right)=\left( {1.87_{-0.73}^{+1.25}\left( {\mathrm{stat}} \right)\pm 0.19\left( {\mathrm{syst}} \right)\pm 0.32\left( {\mathrm{norm}} \right)} \right)\times {10^{-6 }},} \hfill \\ {\,\,{{\mathcal{A}}_{CP }}\left( {{B^{+}}\to D_s^{+}\phi } \right)=-0.01\pm 0.41\left( {\mathrm{stat}} \right)\pm 0.03\left( {\mathrm{syst}} \right).} \hfill \\ \end{array} $
The last uncertainty on
$ \mathcal{B}\left( {{B^{+}}\to D_s^{+}\phi } \right) $
is from the branching fractions of the
$ {B^{+}}\to D_s^{+}{{\overline{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)}^{+}{{\overline{K}}^{*0 }} $
and
$ B_c^{+}\to D_s^{+}\phi $
, including the result
$ \mathcal{B}\left( {{B^{+}}\to {D^{+}}{K^{*0 }}} \right)<1.8\times {10^{-6 }} $
at the 90% credibility level.
A
bstract
A measurement of the inclusive
Z
→ ττ cross-section in
pp
collisions at
$ \sqrt{s}=7\,\mathrm{TeV} $
is presented based on a dataset of 1
.
0 fb
−1
collected by the LHCb detector. ...Candidates for
Z
→ τ τ decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for
Z
bosons, with invariant mass between 60 and 120 GeV
/c
2
, which decay to τ leptons with transverse momenta greater than 20 GeV
/c
and pseudorapidities between 2
.
0 and 4
.
5, is measured to be σ
pp
→Z→
ττ
= 71
.
4 ± 3
.
5 ± 2
.
8 ± 2
.
5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for
Z
→ τ τ to
Z
→
μμ
is determined to be 0
.
93 ± 0
.
09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements.
A
bstract
A study of
$ {D^{+}}K_{\mathrm{S}}^0 $
and
D
0
K
+
final states is performed in a sample of 1.0 fb
−1
of
pp
collision data collected at a centre-of-mass energy of
$ \sqrt{s}=7\;\mathrm{TeV} ...$
with the LHCb detector. We confirm the existence of the
$ D_{s1}^{*}{{\left( {2700} \right)}^{+}} $
and
$ D_{sJ}^{*}{{\left( {2860} \right)}^{+}} $
excited states and measure their masses and widths to be
$ \begin{array}{*{20}{c}} {m\left( {D_{s1}^{*}{{{\left( {2700} \right)}}^{+}}} \right)=2709.2\pm 1.9\left( {\mathrm{stat}} \right)\pm 4.5\left( {\mathrm{syst}} \right)\mathrm{MeV}/{c^2},} \hfill \\ {\varGamma \left( {D_{s1}^{*}{{{\left( {2700} \right)}}^{+}}} \right)=115.8\pm 7.3\left( {\mathrm{stat}} \right)\pm 12.1\left( {\mathrm{syst}} \right)\mathrm{MeV}/{c^2},} \hfill \\ {m\left( {D_{sJ}^{*}{{{\left( {2860} \right)}}^{+}}} \right)=2866.1\pm 1.0\left( {\mathrm{stat}} \right)\pm 6.3\left( {\mathrm{syst}} \right)\mathrm{MeV}/{c^2},} \hfill \\ {\varGamma \left( {D_{sJ}^{*}{{{\left( {2860} \right)}}^{+}}} \right)=69.9\pm 3.2\left( {\mathrm{stat}} \right)\pm 6.6\left( {\mathrm{syst}} \right)\mathrm{MeV}/{c^2}} \hfill \\ \end{array} $
Search for the Bs0 → η′ϕ decay Alkhazov, G.; Alves, A. A.; d’Argent, P. ...
The journal of high energy physics,
31/5, Letnik:
2017, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
A search for the charmless
B
s
0
→
η
′
ϕ
decay is performed using
pp
collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, corresponding to an ...integrated luminosity of 3 fb
−1
. No signal is observed and upper limits on the
B
s
0
→
η
′
ϕ
branching fraction are set to 0
.
82 × 10
−6
at 90% and 1
.
01 × 10
−6
at 95% confidence level.
A
bstract
An amplitude analysis of the decay
Λ
b
0
→
D
0
pπ
−
is performed in the part of the phase space containing resonances in the
D
0
p
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
0
p
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
0
p
amplitude is investigated and found to be consistent with a new resonance, denoted the Λ
c
(2860)
+
, of spin 3
/
2 and positive parity.
A
bstract
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
A
CP
B
0
→
K
*
0
μ
+
μ
−
=
−
0.035
±
0.024
±
0.003
,
A
CP
B
+
→
K
+
μ
+
μ
−
=
0.012
±
0.017
±
0.001
,
where the first uncertainties are statistical and the second are due to systematic effects. Both measurements are consistent with the Standard Model prediction of small
CP
asymmetry in these decays.
A
bstract
Production of
ϒ
mesons in proton-lead collisions at a nucleon-nucleon centre-of-mass energy
s
NN
= 5 TeV is studied with the LHCb detector. The analysis is based on a data sample ...corresponding to an integrated luminosity of 1
.
6 nb
−1
. The
ϒ
mesons of transverse momenta up to 15 GeV/
c
are reconstructed in the dimuon decay mode. The rapidity coverage in the centre-of-mass system is 1
.
5
< y <
4
.
0 (forward region) and −5
.
0
< y <
−2
.
5 (backward region). The forward-backward production ratio and the nuclear modification factor for
ϒ
(1
S
) mesons are determined. The data are compatible with the predictions for a suppression of
ϒ
(1
S
) production with respect to proton-proton collisions in the forward region, and an enhancement in the backward region. The suppression is found to be smaller than in the case of prompt
J/ψ
mesons.
Observation of the Λb0 → J/ψ pπ− decay Ajaltouni, Z.; Albrecht, J.; Anderlini, L. ...
The journal of high energy physics,
22/7, Letnik:
2014, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
The first observation of the Cabibbo-suppressed decay
Λ
b
0
→
J
/
ψpπ
−
is reported using a data sample of proton-proton collisions at 7 and 8 TeV, corresponding to an integrated luminosity ...of 3 fb
−1
. A prominent signal is observed and the branching fraction relative to the decay mode
Λ
b
0
→
J
/
ψpK
−
is determined to be
ℬ
Λ
b
0
→
J
/
ψp
π
−
ℬ
Λ
b
0
→
J
/
ψp
K
−
=
0.0824
±
0.0025
stat
±
0.0042
syst
.
A search for direct
CP
violation is performed. The difference in the
CP
asymmetries between these two decays is found to be
A
CP
Λ
b
0
→
J
/
ψp
π
−
−
A
CP
Λ
b
0
→
J
/
ψp
K
−
=
+
5.7
±
2.4
stat
±
1.2
syst
%
,
which is compatible with
CP
symmetry at the 2.2
σ
level.
PDF