Study of the doubly charmed tetraquark Tcc Abdelmotteleb, A. S. W; Ajaltouni, Z; Andreianov, A ...
Nature communications,
12/2022, Letnik:
13, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar Tcc+ tetraquark with a quark content of ccu¯d¯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector Tcc+ state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the Tcc+ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.The existence and properties of tetraquark states with two heavy quarks and two light antiquarks have been widely debated. Here, the authors use a unitarized model to study the properties of an exotic narrow state compatible with a doubly charmed tetraquark.
Abstract
The SHiP experiment has been proposed at CERN to shed light
on phenomena still unexplained in the framework of the Standard
Model, such as the nature of dark matter, the baryonic asymmetry ...of
the Universe and the neutrino oscillations, searching for hints of
New Physics. A section of the detector will be dedicated to the
study of neutrino physics with special emphasis on tau neutrino
properties, still very poorly measured. A system to identify the
muons produced in neutrino interactions, based on RPC technology,
has been proposed and it is presented in detail in this paper.
Abstract
The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the ...electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.
A
bstract
A precision measurement of the
Z
boson production cross-section at
s
= 13 TeV in the forward region is presented, using
pp
collision data collected by the LHCb detector, corresponding to an ...integrated luminosity of 5.1 fb
−
1
. The production cross-section is measured using
Z → μ
+
μ
−
events within the fiducial region defined as pseudorapidity 2
.
0
< η <
4
.
5 and transverse momentum
p
T
>
20 GeV
/c
for both muons and dimuon invariant mass 60
< M
μμ
<
120 GeV
/c
2
. The integrated cross-section is determined to be
σ
Z
→
μ
+
μ
−
=
196.4
±
0.2
±
1.6
±
3.9
pb
,
where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions within uncertainties.
A
bstract
Four decay modes of the
B
c
+
meson into a
J/ψ
meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at centre-of-mass ...energies of 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb
−
1
. The decay
B
c
+
→ J/ψK
+
K
−
π
+
π
+
π
−
is observed for the first time, and evidence for the
B
c
+
→ J/ψ
4
π
+
3
π
−
decay is found. The decay
B
c
+
→ J/ψ
3
π
+
2
π
−
is observed and the previous observation of the
B
c
+
→ ψ
(2
S
)
π
+
π
+
π
−
decay is confirmed using the
ψ
(2
S
) →
J/ψπ
+
π
−
decay mode. Ratios of the branching fractions of these four
B
c
+
decay channels are measured.
A
bstract
A first search for the lepton-flavour violating decays
B
0
→
K
*0
τ
±
μ
∓
is presented. The analysis is performed using a sample of proton-proton collision data, collected with the LHCb ...detector at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018, corresponding to an integrated luminosity of 9 fb
−
1
. No significant signal is observed, and upper limits on the branching fractions are determined to be
B
B
0
→
K
∗
0
τ
+
μ
−
<
1.0
1.2
×
10
−
5
and
B
B
0
→
K
∗
0
τ
−
μ
+
<
8.2
9.8
×
10
−
6
at the 90% (95%) confidence level.
Observation of the Bs0→ D+D− decay Alessio, F.; Aliouche, Z.; Artamonov, A. ...
The journal of high energy physics,
07/2023, Letnik:
2023, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
The first observation of the
B
s
0
→ D
∗+
D
∗
−
decay and the measurement of its branching ratio relative to the
B
0
→ D
∗+
D
∗
−
decay are presented. The data sample used corresponds to an ...integrated luminosity of 9 fb
−
1
of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with more than 10 standard deviations and the time-integrated ratio of branching fractions is determined to be
B
B
s
0
→
D
∗
+
D
∗
−
B
B
0
→
D
∗
+
D
∗
−
=
0.269
±
0.032
±
0.011
±
0.008
,
where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio
f
s
/f
d
. The
B
s
0
→ D
*+
D
*
−
branching fraction is calculated to be
B
B
s
0
→
D
∗
+
D
∗
−
=
2.15
±
0.26
±
0.09
±
0.06
±
0.16
×
10
−
4
,
where the fourth uncertainty is due to the
B
0
→ D
*
+
D
*−
branching fraction. These results are calculated using the average
B
s
0
meson lifetime in simulation. Correction factors are reported for scenarios where either a purely heavy or a purely light
B
s
0
eigenstate is considered.
We report the direct observation of muon neutrino interactions with the SND@LHC detector at the Large Hadron Collider. A dataset of proton-proton collisions at sqrts=13.6 TeV collected by SND@LHC in ...2022 is used, corresponding to an integrated luminosity of 36.8 fb^{-1}. The search is based on information from the active electronic components of the SND@LHC detector, which covers the pseudorapidity region of 7.2<η<8.4, inaccessible to the other experiments at the collider. Muon neutrino candidates are identified through their charged-current interaction topology, with a track propagating through the entire length of the muon detector. After selection cuts, 8 ν_{μ} interaction candidate events remain with an estimated background of 0.086 events, yielding a significance of about 7 standard deviations for the observed ν_{μ} signal.
A
bstract
A search for the lepton-flavour violating decays
B
0
→
K
*0
μ
±
e
∓
and
B
s
0
→ ϕμ
±
e
∓
is presented, using proton-proton collision data collected by the LHCb detector at the LHC, ...corresponding to an integrated luminosity of 9 fb
−
1
. No significant signals are observed and upper limits of
B
B
0
→
K
∗
0
μ
+
e
−
<
5.7
×
10
−
9
6.9
×
10
−
9
,
B
B
0
→
K
∗
0
μ
−
e
+
<
6.8
×
10
−
9
7.9
×
10
−
9
,
B
B
0
→
K
∗
0
μ
±
e
∓
<
10.1
×
10
−
9
11.7
×
10
−
9
,
B
B
s
0
→
ϕ
μ
±
e
∓
<
16.0
×
10
−
9
19.8
×
10
−
9
are set at 90% (95%) confidence level. These results constitute the world’s most stringent limits to date, with the limit on the decay
B
s
0
→ ϕμ
±
e
∓
the first being set. In addition, limits are reported for scalar and left-handed lepton-flavour violating New Physics scenarios.
