arXiv subjects

Manuel Pavon Valderrama

Publications and source records attributed to Manuel Pavon Valderrama.

47 records · Page 3Linked to original sources

arXiv2018

Heavy-Quark Symmetry Partners of the Pc(4450) Pentaquark

The spectrum of heavy-hadron molecules is constrained by heavy-quark symmetry in its different manifestations. Heavy-quark spin symmetry for instance connects the properties of the ground and excited states of heavy hadrons, while heavy-antiquark-diquark symmetry connects the properties of heavy antimesons ($\bar{D}$, $\bar{D}^*$) and doubly heavy baryons ($Ξ_{cc}$, $Ξ_{cc}^*$). A prediction of these symmetries is that if the $P_c(4450)$ is indeed a $\bar{D}^* Σ_c$ bound state, then there should be a series of $\bar{D}^* Σ_c^*$, $Ξ_{cc} Σ_c$, $Ξ_{cc}^* Σ_c$, $Ξ_{cc} Σ_c^*$ and $Ξ_{cc}^* Σ_c^*$ partners. The concrete application of heavy-quark spin symmetry indicates that, if the $P_c(4450)$ is a $\frac{3}{2}^{-}$ $\bar{D}^* Σ_c$ molecule, the existence of a $\frac{5}{2}^{-}$ $\bar{D}^* Σ_c^*$ partner with similar binding energy --- which we call $P_c(4515)$, given its expected mass --- is likely. Conversely, the application of heavy-antiquark-diquark symmetry indicates that the $0^+$ $Ξ_{cc} Σ_c$, $1^+$ $Ξ_{cc} Σ_c^*$, $2^+$ $Ξ_{cc}^* Σ_c$ and $3^+$ $Ξ_{cc}^* Σ_c^*$ molecules are likely to bind too, with binding energies in the $20-30\,{\rm MeV}$ range.

hep-ph↗

arXiv2018

Exotic Doubly Charmed Ds0(2317)D and Ds1(2460)D* Molecules

The $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ heavy meson systems can exchange a kaon that is emitted in S-wave owing to the opposite intrinsic parity of the $D_{s0}^*$($D_{s1}^*$) and $D$($D^*$) mesons. As a consequence of the mass difference of the $D_{s0}^*$($D_{s1}^*$) and $D$($D^*$) mesons, the range of the kaon exchange potential will be significantly longer than expected, corresponding to an effective mass of about $200\,{\rm MeV}$. The potential will be very strong: the strength of the interaction is proportional to $(m_{D_{s0}} - m_D)^2 / f_π^2$ and $(m_{D_{s1}} - m_{D^*})^2 / f_π^2$. This combination of range and strength almost guarantees the existence of $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ bound states with $J^P = 0^{-}$ and $J^P = 0^{-}, 2^{-}$ respectively. Concrete calculations indicate a binding energy of $5-15\,{\rm MeV}$ independently of $J^P$. The $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ molecules have manifestly exotic flavour quantum numbers: $C=2$, $S=1$ and $I=1/2$. We expect the existence of bottom counterparts composed of the $B B_{s0}$ and $B^* B_{s1}^*$ mesons, which will be more bound and have a richer spectrum that might include a shallow P-wave state and an excited S-wave state.

hep-ph↗

arXiv2018

The $D^* D^* \bar{D}$ and $D^* D^* \bar{D}^*$ Three-Body Systems

The hidden charm $X(3872)$ resonance is usually thought to be a $D^{*0} \bar{D}^0$ meson-antimeson molecule with quantum numbers $J^{PC} = 1^{++}$. If this is the case, there is the possibility that there might be three body bound states with two charmed mesons and a charmed antimeson. Here we argue that the theoretical existence of this type of three body molecules is expected from heavy quark spin symmetry. If applied to the two body sector, this symmetry implies that the interaction of the $D^{*0} \bar{D}^{*0}$ meson-antimeson pair in the $J^{PC} = 2^{++}$ channel is the same as in the $J^{PC} = 1^{++}$ $D^{*0} \bar{D}^0$ case. From this we can infer that the $J^P = 3^{-}$ $D^{*0} D^{*0} \bar{D}^{*0}$ molecule will be able to display the Efimov effect if the scattering length of the $2^{++}$ channel is close enough to the unitary limit. Heavy quark spin symmetry also indicates that the $J^P = 2^{-}$ $D^{*0} D^{*0} \bar{D}^0$ molecule is analogous to the $J^P = 3^{-}$ $D^{*0} D^{*0} \bar{D}^{*0}$ one. That is, it can also have a geometric spectrum. If we consider these triply heavy trimers in the isospin symmetric limit, the Efimov effect disappears and we can in principle predict the fundamental state of the $2^-$ $D^*D^*\bar{D}$ and $3^-$ $D^* D^* \bar{D}^*$ systems. The same applies to the $B^*B^* \bar{B}^*$ system: if the $Z_b(10650)$ is an isovector $B^* \bar{B}^*$ molecule then the $0^-$ isodoublet and the $1^-$, $2^-$ isoquartet $B^* B^* \bar{B}^*$ trimers might bind, but do not display Efimov physics. Finally from heavy flavour symmetry it can be argued that scattering in the $B D$ two-body system might be resonant. This would in turn imply the possibility of Efimov physics in the $B B D$ three body system.

hep-ph↗

arXiv2018

Scale Invariance in Heavy Hadron Molecules

We discuss a scenario in which the $P_c(4450)^{+}$ heavy pentaquark is a $Σ_c \bar{D}^*$-$Λ_{c}(2595) \bar{D}$ molecule. The $Λ_{c1} \bar{D} \to Σ_c \bar{D}^*$ transition is mediated by the exchange of a pion almost on the mass shell that generates a long-range $1/r^2$ potential. This is analogous to the effective force that is responsible for the Efimov spectrum in three-boson systems interacting through short-range forces. The equations describing this molecule exhibit approximate scale invariance, which is anomalous and broken by the solutions. If the $1/r^2$ potential is strong enough this symmetry survives in the form of discrete scale invariance, opening the prospect of an Efimov-like geometrical spectrum in two-hadron systems. For a molecular pentaquark with quantum numbers $\frac{3}{2}^{-}$ the attraction is not enough to exhibit discrete scale invariance, but this prospect might very well be realized in a $\frac{1}{2}^{+}$ pentaquark or in other hadron molecules involving transitions between particle channels with opposite intrinsic parity and a pion near the mass shell. A very good candidate is the $Λ_{c}(2595) \barΞ_b - Σ_c \barΞ_b'$ molecule. Independently of this, the $1/r^2$ force is expected to play a very important role in the formation of this type of hadron molecule, which points to the existence of $\frac{1}{2}^{+}$ $Σ_c D^*$-$Λ_{c}(2595) D$ and $1^+$ $Λ_{c}(2595) Ξ_b - Σ_c Ξ_b'$ molecules and $0^{+}$/$1^{-}$ $Λ_{c}(2595) \barΞ_b - Σ_c \barΞ_b'$ baryonia.

hep-ph↗

arXiv2018

$D Ξ$ and $D^* Ξ$ Molecular States from One Boson Exchange

We explore the existence of $D Ξ$ and $D^* Ξ$ molecular states within the one boson exchange model. We regularize the potential derived in this model with a form factor and a cut-off of the order of $1\,{\rm GeV}$. To determine the cut-off, we use the condition that the $X(3872)$ is reproduced as a pole in the $J^{PC} = 1^{++}$ $D^*\bar{D}$ amplitude. From this we find that the $J^P= {\frac{1}{2}}^{-}$ $D^*\,Ξ$ system is on the verge of binding and has an unnaturally large scattering length. For the $J^P= {\frac{1}{2}}^{-}$ $D\,Ξ$ and the $J^P= {\frac{3}{2}}^{-}$ $D^*\,Ξ$ systems the attraction is not enough to form a bound state. From heavy quark symmetry and the quark model we can extend the previous model to the $P Ξ_{QQ}$ and $P^* Ξ_{QQ}$ systems, with $P = D, \bar{B}$, $P^* = D^*, \bar{B}^*$ and $Ξ_{QQ} = Ξ_{cc}, Ξ_{bb}$. In this case we predict a series of triply heavy pentaquark-like molecules.

hep-ph↗

arXiv2018

Three-Body $J^P = 0^+,1^+,2^+$ $B^* B^* \bar{K}$ Bound States

Three body systems with short-range interactions display universal features that have been extensively explored in atomic physics, but apply to hadron physics as well. Systems composed of two non-interacting identical particles (species H) of mass $M$ and a third particle (species P) of mass $m$ that interacts attractively with the other two have the property that they are more likely to bind for larger values of the mass ratio $M/m$. This is particularly striking if the HHP system is in P-wave (while the interacting pair is in S-wave), in which case one would not normally expect the formation of a three body state. If we assume that the $B^* \bar{K}$ binds to form the $B^*_{s1}$ heavy meson and notice that the mass ratio of the $B^*$ to $\bar{K}$ is $M /m = 10.8$, concrete calculations indicate that there should be a three body $B^* B^* \bar{K}$ bound state between $30-40\,{\rm MeV}$ below the $B^*_{s1} B^*$ threshold. For the $Ξ_{bb} Ξ_{bb} \bar{K}$ system the mass imbalance is about $M /m = 20.5$ and two bound states are expected to appear, a fundamental and an excited one located at $50-90$ and $5-15\,{\rm MeV}$ below the $Ξ_{bb} Ω^*_{bb\frac{1}{2}}$ threshold (where $Ω^*_{bb\frac{1}{2}}$ denotes the $Ξ_{bb} \bar{K}$ bound state). We indicate the possibility of analogous P-wave three body bound states composed of two heavy baryons and a kaon or antikaon and investigate the conditions under which the Efimov effect could appear in these systems.

hep-ph↗

arXiv2018

Are there near-threshold Coulomb-like Baryonia?

The $Λ_c(2590) Σ_c$ system can exchange a pion near the mass-shell. Owing to the opposite intrinsic parity of the $Λ_c(2590)$ and $Σ_c$, the pion is exchanged in S-wave. This gives rise to a Coulomb-like force that might be able to bind the system. If one takes into account that the pion is not exactly on the mass shell, there is a shallow S-wave state, which we generically call the $Y_{cc}(5045)$ and $Y_{c\bar c}(5045)$ for the $Λ_c(2590) Σ_c$ and $Λ_c(2590) \barΣ_c$ systems respectively. For the baryon-antibaryon case this Coulomb-like force is independent of spin: the $Y_{c\bar c}(5045)$ baryonia will appear either in the spin $S=0$ or $S=1$ configurations with G-parities $G=(-1)^{L+S+1}$. For the baryon-baryon case the Coulomb-like force is attractive in the spin $S=0$ configuration, for which a doubly charmed molecule is expected to form near the threshold. This type of spectrum might be very well realized in other molecular states composed of two opposite parity hadrons with the same spin and a mass difference close to that of a pseudo-Goldstone boson, of which a few examples include the $Λ(1405) N$, $Λ(1520) Σ^*$, $Ξ(1690) Σ$, $D_{s0}^*(2317) D$ and $D_{s1}^*(2460) D^*$ molecules.

hep-ph↗

arXiv2017

Power Counting and Wilsonian Renormalization in Nuclear Effective Field Theory

Effective field theories are the most general tool for the description of low energy phenomena. They are universal and systematic: they can be formulated for any low energy systems we can think of and offer a clear guide on how to calculate predictions with reliable error estimates, a feature that is called power counting. These properties can be easily understood in Wilsonian renormalization, in which effective field theories are the low energy renormalization group evolution of a more fundamental ---perhaps unknown or unsolvable--- high energy theory. In nuclear physics they provide the possibility of a theoretically sound derivation of nuclear forces without having to solve quantum chromodynamics explicitly. However there is the problem of how to organize calculations within nuclear effective field theory: the traditional knowledge about power counting is perturbative but nuclear physics is not. Yet power counting can be derived in Wilsonian renormalization and there is already a fairly good understanding of how to apply these ideas to non-perturbative phenomena and in particular to nuclear physics. Here we review a few of these ideas, explain power counting in two-nucleon scattering and reactions with external probes and hint at how to extend the present analysis beyond the two-body problem.

nucl-th↗

arXiv2014

Detecting the long-distance structure of the X(3872)

We study the X(3872)-->D^0 \bar D^0 π^0 decay within a D \bar D^* molecular picture for the X(3872) state. This decay mode is more sensitive to the long-distance structure of the X(3872) resonance than its J/ψππand J/\psi3πdecays, which are mainly controlled by the details of the X(3872) wave function at short distances. We show that the D^0 \bar D^0 final state interaction can be important, and that a precise measurement of this partial decay width can provide valuable information on the interaction strength between the D^{(*)} \bar D^{(*)} charm mesons.

hep-ph↗

arXiv2013

Consequences of Heavy Quark Symmetries for Hadronic Molecules

Among the newly observed structures in the heavy quarkonium mass region, some are proposed to be hadronic molecules. We investigate the consequences of heavy quark flavor symmetry on these heavy meson hadronic molecules. The symmetry allows us to predict new hadronic molecules on one hand, and test the hadronic molecular assumption of the observed structures on the other hand. We explore the consequences of the flavor symmetry assuming the X(3872) and $Z_b(10610)$ as a isoscalar $D\bar D^*$ and isovector $B\bar B^*$ hadronic molecule, respectively. A series of hadronic molecules composed of heavy mesons are predicted. In particular, there is an isoscalar $1^{++}$ $B\bar B^*$ bound state with a mass of 10580 MeV which may be searched for in the $Υ(1S,2S)π^+π^-π^0$ mass distribution; the isovector charmonium partners of the $Z_b(10610)$ and the $Z_b(10650)$ are also predicted, one of which probably corresponds to the very recently observed $Z_c(3900)$ and $Z_c(4025)$ resonances by the BESIII Collaboration.

hep-ph↗

arXiv2013

Heavy Antiquark--Diquark Symmetry and Heavy Hadron Molecules: Are There Triply Heavy Pentaquarks?

We explore the consequences of heavy flavour, heavy quark spin and heavy antiquark-diquark symmetries for hadronic molecules within an effective field theory framework.. Owing to heavy antiquark-diquark symmetry, the doubly heavy baryons have approximately the same light-quark structure as the heavy antimesons. As a consequence, the existence of a heavy meson-antimeson molecule implies the possibility of a partner composed of a heavy meson and a doubly-heavy baryon. In this regard, the D\bar D* molecular nature of the X(3872) will hint at the existence of several baryonic partners with isospin I=0 and J^P = 5/2^- or 3/2^-. Moreover, if the Zb(10650) turns out to be a B*\bar B* bound state, we can be confident of the existence of \Xibb* \bar B* hadronic molecules with quantum numbers I(J^P) = 1(1/2^-) and I(J^P) = 1(3/2^-). These states are of special interest since they can be considered to be triply-heavy pentaquarks.

hep-ph↗