SU(6)lsf×HQSS模型中的奇异激发态研究

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"在SU（6）lsf-HQSS模型内研究了α激发态，该模型结合了手性和重夸克自旋对称性，成功解释了C = 1，S = -2和I = 0部门的低能奇偶共振。文章详细探讨了Romanets等人提出的统一耦合通道模型中的重归一化程序，该程序对于理解最近LHCb合作观察到的五个c（^）状态至关重要。这些状态中的一些可能具有奇偶校验且J = 1/2或J = 3/2，它们属于SU（6）轻子味-重夸克自旋对称性（light-spin-flavor）的同一个双倍组，成为charm和beauty的重子。文章为开放访问，可在Eur.Phys.J.C (2018) 78:114上查阅。" 这篇摘要讨论了一个理论物理领域的研究，主要关注于粒子物理学中的重子激发态。研究者们回顾并应用了Romanets等人在2012年提出的统一耦合通道模型中的重归一化方法，该方法特别适用于C荷为1，同位旋为-2的系统。近期，LHCb实验合作组在这一领域发现了五个新的c（^）态，即含有粲夸克的重子。研究者表明，模型中的介子-重子相互作用符合手性和重夸克自旋对称性原则，这使得模型能够成功地解释观测到的最低能奇偶共振，例如Îc（2595）和Î› c（2625），以及b（5912）和b（5920）。进一步的研究发现，LHCb实验观察到的一些状态可能具有奇偶性，其自旋量子数可以是1/2或3/2。这些状态被归类在SU（6）轻子味-重夸克自旋对称性（light-spin-flavor × Heavy Quark Spin Symmetry, HQSS）框架下的一个双倍组，这意味着它们可能是charm和beauty重子的成员。这个发现对于理解这些奇异重子的性质和分类提供了重要的理论依据。该研究论文发表在《欧洲物理杂志C》（Eur.Phys.J.C）上，并标记为“Open Access”，意味着公众可以免费获取和阅读全文。作者包括来自西班牙瓦伦西亚的Instituto de Física Corpuscular、德国法兰克福大学的Institut für Theoretische Physik等多个研究机构的专家。文章的接收日期为2017年12月，接受日期为2018年1月，且遵循了开放获取出版的原则，为粒子物理学领域的研究提供了宝贵的贡献。

Eur. Phys. J. C (2018) 78:114

https://doi.org/10.1140/epjc/s10052-018-5597-3

Regular Article - Theoretical Physics



excited states within a SU(6)

lsf

× HQSS model

J. Nieves

,R.Pavao

, L. Tolos

2,3,4,5,a

Instituto de Física Corpuscular (centro mixto CSIC-UV), Institutos de Investigación de Paterna, Aptdo. 22085, 46071 Valencia, Spain

Institut für Theoretische Physik, University of Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany

Frankfurt Institute for Advanced Studies, University of Frankfurt, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main, Germany

Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans, 08193 Barcelona, Spain

Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain

Received: 1 December 2017 / Accepted: 26 January 2018

Abstract We have reviewed the renormalization procedure

used in the unitarized coupled-channel model of Romanets

et al. (Phys Rev D 85:114032, 2012), and its impact in the

C = 1, S =−2, and I = 0 sector, where ﬁve 

(∗)

states

have been recently observed by the LHCb Collaboration. The

meson-baryon interactions used in the model are consistent

with both chiral and heavy-quark spin symmetries, and lead

to a successful description of the observed lowest-lying odd

parity resonances 

(2595) and 

(2625), and 

(5912)

and 

(5920) resonances. We show that some (probably at

least three) of the states observed by LHCb will also have odd

parity and J = 1/2orJ = 3/2, belonging two of them to

the same SU(6)

light-spin-ﬂavor

×HQSS multiplets as the latter

charmed and beauty  baryons.

1 Introduction

The LHCb Collaboration [1] has recently reported the exis-

tence of ﬁve 

states, analyzing the 

−

spectrum in

pp collisions, with masses ranging between 3 and 3.1 GeV.

These results have renewed the interest in baryon spec-

troscopy, with the long-standing question whether these

states can be accommodated within the quark model pic-

ture and/or qualify better as being dynamically generated via

hadron-hadron scattering processes.

Earlier predictions for such states have been reported

within conventional quark models [2–13]. The experimental

discovery of the ﬁve 

states has triggered a large activity in

the ﬁeld, and thus some quark models have been revisited in

view of the new results [14–20], suggestions as pentaquarks

have been advocated [21–25], models based on QCD sum-

rules have been put to test [26–32], or quark-soliton models

e-mail: tolos@th.physik.uni-frankfurt.de

have been employed [33]. Also, Lattice QCD has reported

results on the spectroscopy of 

states [34].

Within molecular models, there have been previous pre-

dictions on 

states [35–38]. In Ref. [36] several reso-

nant states were obtained with masses much below 3 GeV,

by employing a zero-range exchange of vector mesons as

the bare interaction for the s-wave baryon-meson scatter-

ing. Similar qualitative results were obtained in Ref. [35],

where ﬁnite range effects were considered. Lately the work

of Ref. [39] has revisited Ref. [36], ﬁnding that, after mod-

ifying the regularization scheme with physically motivated

parameters, two 

resonant states were generated at 3050

and 3090 MeV with spin-parity J

= 1/2

−

, reproducing

the masses and widths of two of the experimental states.

More recently, the 

states have been also investigated using

an extended local hidden gauge approach [40]. Within this

scheme, low-lying 1/2

and 3/2

baryons, as well as pseu-

doscalar and vector mesons, are considered to construct the

baryon-meson coupled channel space. In this manner, two



states of J

= 1/2

−

and one 

∗

= 3/2

−

can be

identiﬁed, the ﬁrst two in good agreement with the results of

[39] and the third one fairly well.

The use of the hidden-gauge formalism allows for the

preservation of heavy-quark spin symmetry (HQSS), which

is a proper QCD symmetry that appears when the quark

masses, such as that of the charm quark, become larger than

the typical conﬁnement scale. Aiming to incorporate explic-

itly HQSS, a scheme was developed in Refs. [37,38,41–

43] that implements a consistent SU(6)

lsf

× SU(2)

HQSS

extension of the Weinberg–Tomozawa (WT) π N interac-

tion, where “lsf” stands for light quark-spin-ﬂavor sym-

metry, respectively. Indeed, the works of Refs. [37,38]are

the ﬁrst meson-baryon molecular studies, fully consistent

with HQSS, of the well-established odd-parity 

(2595)

[J = 1/2] and 

(2625) [J = 3/2] resonances.

123

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