The production of J/ψ mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair sNN=8.16 TeV with the LHCb detector at the LHC. The double differential cross-sections ...of prompt and nonprompt J/ψ production are measured as a function of the J/ψ transverse momentum and rapidity in the nucleon–nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
A search is presented for massive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8 TeV, corresponding ...to integrated luminosities of 1 and 2
fb
-
1
, respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80
GeV
/
c
2
and lifetimes from 5 to 100
ps
are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23–198 GeV/
c
2
range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.
A search is presented for long-lived particles with a mass between 25 and 50
GeV
/
c
2
and a lifetime between 2 and 500 ps, using proton–proton collision data corresponding to an integrated ...luminosity of 2.0
fb
-
1
, collected by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are assumed to be pair-produced in the decay of a 125
GeV
/
c
2
Standard-Model-like Higgs boson. The experimental signature is a single long-lived particle, identified by a displaced vertex with two associated jets. No excess above background is observed and limits are set on the production cross-section as a function of the mass and lifetime of the long-lived particle.
A
bstract
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb
−1
, collected with the LHCb detector between 2011 and 2018, a new narrow charmonium state, the X(3842) ...resonance, is observed in the decay modes
$$ \mathrm{X}(3842)\to {D}^0{\overline{D}}^0 $$
X
3842
→
D
0
D
¯
0
and X(3842) →
D
+
D
−
. The mass and the natural width of this state are measured to be
$$ \begin{array}{l}{m}_{X(3842)}=3842.71\pm 0.16\pm 0.12\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{X(3842)}=2.79\pm 0.51\pm 0.35\ MeV,\hfill \end{array} $$
m
X
3842
=
3842.71
±
0.16
±
0.12
M
e
V
/
c
2
,
Γ
X
3842
=
2.79
±
0.51
±
0.35
M
e
V
,
where the first uncertainty is statistical and the second is systematic. The observed mass and narrow natural width suggest the interpretation of the new state as the unobserved (spin-3
ψ
3
1
3
D
3
) charmonium state.
In addition, prompt hadroproduction of the
ψ
(3770) and
χ
2
(3930) states is observed for the first time, and the parameters of these states are measured to be
$$ \begin{array}{l}{m}_{\psi (3770)}=3778.1\pm 0.7\pm 0.6\ MeV/{c}^2,\hfill \\ {}{m}_{\chi_2(3930)}=3921.9\pm 0.6\pm 0.2\ MeV/{c}^2,\hfill \\ {}{\varGamma}_{\chi_2(3930)}=36.6 \pm 1.9 \pm 0.9\ MeV,\hfill \end{array} $$
m
ψ
3770
=
3778.1
±
0.7
±
0.6
M
e
V
/
c
2
,
m
χ
2
3930
=
3921.9
±
0.6
±
0.2
M
e
V
/
c
2
,
Γ
χ
2
3930
=
36.6
±
1.9
±
0.9
M
e
V
,
where the first uncertainty is statistical and the second is systematic.
A
bstract
The cross-sections of exclusive (coherent) photoproduction
J/ψ
and
ψ
(2S) mesons in ultra-peripheral PbPb collisions at a nucleon-nucleon centre-of-mass energy of 5
.
02 TeV are measured ...using a data sample corresponding to an integrated luminosity of 228 ± 10 μb
−
1
, collected by the LHCb experiment in 2018. The differential cross-sections are measured separately as a function of transverse momentum and rapidity in the nucleus-nucleus centre-of-mass frame for
J/ψ
and
ψ
(2S) mesons. The integrated cross-sections are measured to be
σ
J
/
ψ
coh
= 5
.
965
±
0
.
059
±
0
.
232
±
0
.
262 mb and
σ
ψ
2
S
coh
= 0
.
923
±
0
.
086
±
0
.
028
±
0
.
040 mb, where the first listed uncertainty is statistical, the second systematic and the third due to the luminosity determination. The cross-section ratio is measured to be
σ
ψ
2
S
coh
/
σ
J
/
ψ
coh
= 0
.
155
±
0
.
014
±
0
.
003, where the first uncertainty is statistical and the second is systematic. These results are compatible with theoretical predictions.
Measurements of CP observables in B±→DK± and B±→Dπ± decays are presented where the D meson is reconstructed in the final states K±π∓, π±K∓, K+K−, π+π−, K±π∓π+π−, π±K∓π+π− and π+π−π+π−. This analysis ...uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb−1. Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind.
A
bstract
The CKM angle
γ
is determined from
CP
-violating observables measured in
B
±
→
D
K
∓
π
±
π
±
π
∓
h
±
, (
h
=
K, π
) decays, where the measurements are performed in bins of the decay ...phase-space of the
D
meson. Using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7
,
8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb
−
1
,
γ
is determined to be
γ
=
54.8
+
6.0
−
5.8
+
0.6
−
0.6
+
6.7
−
4.3
∘
,
where the first uncertainty is statistical, the second systematic and the third from the external inputs on the coherence factors and strong phases of the
D
-meson decays.
A measurement of ∆Γs Agapopoulou, C.; Alessio, F.; Aliouche, Z. ...
The journal of high energy physics,
22/5, Letnik:
2024, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
Using a dataset corresponding to 9 fb
−
1
of integrated luminosity collected with the LHCb detector between 2011 and 2018 in proton-proton collisions, the decay-time distributions of the ...decay modes
B
s
0
→
J
/
ψη
′
and
B
s
0
→
J
/
ψ
π
+
π
−
are studied. The decay-width difference between the light and heavy mass eigenstates of the
B
s
0
meson is measured to be ∆Γ
s
= 0
.
087 ± 0
.
012 ± 0
.
009 ps
−
1
, where the first uncertainty is statistical and the second systematic.
A
bstract
The
CP
asymmetries of seven
B
−
decays to two charm mesons are measured using data corresponding to an integrated luminosity of 9 fb
−
1
of proton-proton collisions collected by the LHCb ...experiment. Decays involving a
D
*0
or
D
s
∗
−
meson are analysed by reconstructing only the
D
0
or
D
s
−
decay products. This paper presents the first measurement of
A
CP
(
B
−
→
D
s
∗
−
D
0
) and
A
CP
(
B
−
→
D
s
−
D
∗
0
), and the most precise measurement of the other five
CP
asymmetries. There is no evidence of
CP
violation in any of the analysed decays. Additionally, two ratios between branching fractions of selected decays are measured.
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