finite size of a doubly heavy diquark yields a positive correction to baryon masses calculated in the local-diquark approximation. Upon evaluating this correction for the ground states of doubly ...charmed baryons, it became possible to obtain new predictions of importance for current searches of these baryons in LHCb experiments:
m
Ξ
c
c
1
/
2
+
+
≈
m
Ξ
c
c
1
/
2
+
+
= 3615 ± 55 MeV and
m
Ξ
c
c
3
/
2
+
+
≈
m
Ξ
c
c
3
/
2
+
+
3747 ± 55 MeV
The reconstruction efficiency of photons and neutral pions is measured using the relative yields of reconstructed B{sup +} → J/ψK{sup *+}(→ K{sup +}π{sup 0}) and B{sup +} → J/ψK{sup +} decays. The ...efficiency is studied using the data set, corresponding to an integrated luminosity of 3 fb{sup –1}, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV.
The LHCb experiment takes data at the Large Hadron Collider at CERN. During the 2009–2012 running period the performances of the detector have been assessed with pp collision data. The tracking and ...particle identification capabilities reached and exceeded the design specifications, despite the harsher conditions. The LHCb detector operation and its performance are discussed as measured in data from the first LHC run.
Data from the LHCb experiments are indicative of a substantial distinction between the
B
→
K
(or
K
*) +
e
+
e
−
and
B
→
K
(or
K
*) +
μ
+
μ
−
branching ratios (April 2017). The branching ratio for the ...e+e− channel is substantially greater than that for the
μ
+
μ
−
channel, whereas Standard Model (SM) calculations require that they be equal to each other. The above distinction may suggest the existence of a new interaction changing generations and discriminating between leptons that has couplings that are much greater than and are inverse in strength to the SM fermion couplings to the Higgs boson. Under conditions of spontaneously violated mirror symmetry, the coupling of SM particles to the second Higgs scalar that is inevitably present there and which is in principle heavy possesses precisely these properties. An inverse character of this coupling and its strength are not an additional hypothesis but a necessary condition for qualitatively reproducing, in addition, the observed charged-lepton mass hierarchy and the structure of weak lepton mixing—the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) matrix. Within the mirror model being considered, all properties of the new interaction, including its inverse character, are due to the hierarchical character of the quark and charged-lepton mass spectrum.
Z+(4430): Nonexotic interpretation Uglov, T. V.; Pakhlov, P. N.
Physics of atomic nuclei,
03/2016, Letnik:
79, Številka:
2
Journal Article
Recenzirano
The possibility of describing the charged charmonium-like state
Z
+
(4430) as the kinematical rescattering effect is examined. This approach makes it possible to avoid the introduction of exotic ...hadron states in the model, and one describes structures in the ψ(2
S
)π
+
mass spectrum by the presence of the
D
s
(*)′
resonance in a hidden intermediate state. The resulting model predictions are compared with the results obtained by the LHCb Collaboration.
Radiative decays at LHCb Giubega, L. E.
Physics of atomic nuclei,
12/2016, Letnik:
79, Številka:
11-12
Journal Article
Recenzirano
Precise measurements on rare radiative B decays are performed with the LHCb experiment at LHC. The LHCb results regarding the ratio of branching fractions for two radiative decays,
B
0
→
K
*0
γ
and
B
...s
→ ϕ
γ
, the direct
CP
asymmetry in
B
0
→
K
*0
γ
decay channel and the observation of the photon polarization in the
B
±
→
K
±
π
∓
π
±
γ
decay, are included. The first two measurements were performed in 1 fb
–1
of
pp
collisions data and the third one in 3 fb
–1
of data, respectively.
The first ever observation of the decay process
B
0
→
J
/ψη′ is described. The branching ratios were measured for the decay processes
B
(s)
→ J/ψη(′), and the η–η′ mixing angles were determined on ...this basis. The first indication of the occurrence of the decay process
B
s
→ ψ(2
S
)η′ is presented. The respective analysis was performed on the basis of data accumulated with the LHCb detector in proton–proton collisions at the c.m. collision energies of 7 and 8 TeV and the integrated luminosity of 3 fb
−1
.
X(3872): Status and prospects Aushev, T. A.-Kh
Physics of atomic nuclei,
01/2016, Letnik:
79, Številka:
1
Journal Article
Recenzirano
The most recent experimental results obtained by studying the
X
(3872) state in the CLEO-c, LHCb, and BESIII experiments are surveyed, and prospects of its further studies are discussed.
Le sujet de cette thèse porte sur l’étude de la désintégration faible du baryon beau Λb → Λ J/Ψ avec le détecteur LHCb. Cette étude offre la possibilité de tester, d’une part, la validité de la ...symétrie CP dans le secteur baryonique et, d’autre part, celle de la symétrie de renversement du temps T dont les preuves expérimentales de sa violation sont limitées. L’accent est mis sur la mesure des composantes des vecteurs-polarisations du Λb et des résonances intermédiaires Λ et J/Ψ, dont certaines du type ”T-odd” (impaires par T) représentent un signe clair de violation directe de T. Le développement d’un modèle phénoménologique des désintégrations Λb → Λ J/Ψ dans le cadre du formalisme d’hélicité de Jacob-Wick et de Jackson conduit aux calculs de distributions angulaires qui permettent de déduire les valeurs des composantes des vecteurs-polarisations. Une étude approfondie de la reconstruction et de la sélection des données enregistrées par LHCb en 2011 et 2012 est exposée, ainsi qu’une simulation Monte-Carlo complète. La compatibilité entre les valeurs mesurées des vecteurs-polarisation du Λb et du Λ ̄b implique l’absence de violation de CP. La violation directe de la symétrie T n’a pas non plus été observée dans les désintégrations hadroniques du Λb (Λ ̄b). Sur un autre plan, les premières mesures des polarisations longitudinales du Λb et du Λ ̄b ainsi que de la polarisation longitudinale du méson-vecteur J/Ψ ont été réalisées dans le cadre de ce travail.
This thesis subject focuses on the study of the weak decay of the beauty baryon Λb →Λ J/Ψ with the LHCb detector. Firstly, it offers the opportunity to test the validity of the CP symmetry in the baryon sector and, secondly, the one of time-reversal symmetry T whose experimental evidence is tiny. Emphasis is put on the measurement of the components of the polarization-vectors of the Λb and the ones of the intermediate resonances Λ and J/Ψ, whose some components exhibit a clear sign of direct T violation. The development of a phenomenological model of the Λb → Λ J/Ψ decay in the framework of the helicity formalism of Jacob-Wick and Jackson leads to the calculations of the angular distributions which allow to deduce the values of the polarization vector components. A thorough study of the reconstruction and the selection of the data recorded by LHCb in 2011 and 2012 is exposed, as well as a full Monte Carlo simulation. The compatibility between the measured values of the polarization-vector of Λb and Λ ̄b implies the absence of CP violation. The direct violation of the T symmetry has not been observed in the hadronic decays of Λb ( Λ ̄b). On another side, first measurements of the longitudinal polarization of Λb and of Λ ̄b well as the longitudinal polarization of the vector-meson J/Ψ have been performed in the context of this work.
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