arXiv subjects

P. G. Ortega

Publications and source records attributed to P. G. Ortega.

26 records · Page 2Linked to original sources

arXiv2015

Puzzles in quarkonium hadronic transitions with two pion emission

The anomalously large rates of some hadronic transitions from quarkonium are studied using QCD multipole expansion (QCDME) in the framework of a constituent quark model which has been successful in describing hadronic phenomenology. The hybrid intermediate states needed in the QCDME method are calculated in a natural extension of our constituent quark model based on the Quark Confining String (QCS) scheme. Some of the anomalies are explained due to the presence of an hybrid state with a mass near the mass of the decaying resonance whereas other are justified by the presence of molecular components in the wave function. Some unexpected results are pointed out.

hep-ph↗

arXiv2013

Molecular Structures in Hidden Charm Meson and Charmed Baryon Spectrum

Using a constituent quark model we study the mass and decay channels of meson meson and meson baryon structures in the charm sector. We show that the $X(3872)$ and $X(3940)$ resonances can be described as mixed charmonium-molecular states with $J^{PC}=1^{++}$, whereas the $X(3915)$ and the $Y(3940)$ can be assigned to similar mixed states with $J^{PC}=0^{++}$. In the baryon spectrum we identify the $Λ^+_c(2940)$ as a $D^*N$ molecule with $(I)J^P=(0)3/2^-$ and the recently reported $X_c(3250)$ as a $D^*Δ$ resonance with $(I)J^P=(1)5/2^-$ or $(I)J^P=(2)3/2^-$.

hep-ph↗

arXiv2013

Extended calibration range for prompt photon emission in ion beam irradiation

Monitoring the dose delivered during proton and carbon ion therapy is still a matter of research. Among the possible solutions, several exploit the measurement of the single photon emission from nuclear decays induced by the irradiation. To fully characterize such emission the detectors need development, since the energy spectrum spans the range above the MeV that is not traditionally used in medical applications. On the other hand, a deeper understanding of the reactions involving gamma production is needed in order to improve the physic models of Monte Carlo codes, relevant for an accurate prediction of the prompt-gamma energy spectrum.This paper describes a calibration technique tailored for the range of energy of interest and reanalyzes the data of the interaction of a 80MeV/u fully stripped carbon ion beam with a Poly-methyl methacrylate target. By adopting the FLUKA simulation with the appropriate calibration and resolution a significant improvement in the agreement between data and simulation is reported.

physics.med-ph↗

arXiv2012

Quark model description of the Λ_c(2940)^+ as a molecular D^*N state and the possible existence of the Λ_b(6248)

The Λ_c(2940)^+ baryon is studied in a constituent quark model as a molecular state composed by nucleons and D^* mesons. A bound state with the right binding energy is found for the J^π=3/2^- channel. The partial widths Λ_c(2940)^+\to ND and Λ_c(2940)^+\to Σ_c πare calculated and the results are consistent with the experimental data. Additionally a bottom partner \bar B^*N is predicted with a mass of 6248 MeV/c^2.

hep-ph↗

arXiv2012

Molecular structures in charmonium spectrum: The $XYZ$ puzzle

We study in the framework of a constituent quark model the possible contributions of molecular structures to the XYZ charmonium like states. We analyze simultaneously the $c\bar{c}$ structures and the possible molecular components in a formalism which allows us to treat channels below and above thresholds. The only molecular state found in the $1^{++}$ sector correspond to the X(3872). Molecular resonances also appear with other quantum numbers. So, the so called Y(3940) and the X(3915) are suggested to be $J^{PC}=0^{++}$ charmonium states. In the $J^{PC}=1^{--}$ sector we also found significant contributions of the molecular structures which can affect the phenomenology.

hep-ph↗

arXiv2011

Molecular effects in Charmonium Spectrum

We study the influence of possible molecular structures in the charmonium spectrum. We focus on the $0^{++}$ and $1^{--}$ sectors. In the first one we coupled the $2 ^3P_0$ $q\bar q$ pair with $DD$, $J/ψω$, $D_sD_s$ and $J/ψϕ$ channels and we obtain two states compatibles with the X(3945) and the Y(3940). In the second one we include the $3^3S_1$ and $2^3D_1$ charmonium states coupled to $DD$, $DD^*$, $D^*D^*$, $D_sD_s$, $D_sD_s^*$ and $D_s^*D_s^*$. In this calculation we obtain a new molecular state that could be the G(3900) or the controversial Y(4008) and two $c\bar c$ states dressed by the molecular components assigned to the $ψ(4040)$ and the $ψ(4160)$. The two $c\bar c$ states show interesting properties and in particular they solve the strong disagreement of the decay branching ratios measured by BABAR.

hep-ph↗

arXiv2010

Coupled channel approach to the structure of the X(3872)

We have performed a coupled channel calculation of the $1^{++}$ $c\bar c$ sector including $q\bar q$ and $DD^*$ molecular configurations. The calculation was done within a constituent quark model which successfully describes the meson spectrum, in particular the $c\bar c$ $1^{--}$ sector. Two and four quark configurations are coupled using the $^3P_0$ model. The elusive X(3872) meson appears as a new state with a high probability for the $DD^*$ molecular component. When the mass difference between neutral and charged states is included a large $D^0 {D^*}^0$ component is found which dominates for large distances and breaks isospin symmetry in the physical state. The original $c\bar c(2 ^3P_1)$ state acquires a sizable $DD^*$ component and can be identified with the X(3940). We study the $B\to K π^+ π^-J/ψ$ and $B\to K D^0 D^{*0}$ decays finding a good agreement with Belle and BaBar experimental data.

hep-ph↗

arXiv2010

The X(3872) and other possible $XYZ$ molecular states

We perform a coupled channel calculation of the $DD^*$ and $c\bar c$ sectors in the framework of a constituent quark model. The interaction for the $DD^*$ states is obtained using the Resonant Group Method (RGM) and the underlying quark interaction model. The coupling with the two quark system is performed using the $^3 P_0$ model. The X(3872) is found as a molecular state with a sizable $c\bar c$ component. A comparison with Belle and BaBar data has been done, finding a good agreement. Other possible molecular molecular states are discussed.

hep-ph↗