反质子-核碰撞生成Λc+超核：理论研究与实验前景

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"这篇研究论文探讨了在反质子-核碰撞中生成Λc+超核的现象，特别是在反质子-O16碰撞中产生OΛc+ 16超核的过程。研究人员使用了一种基于有效拉格朗日方法的完全协变模型来分析这一过程。在该模型中，Λc-Λc+生成顶点通过反质子与目标核质子的t通道D0和D⁎0介子交换来描述。夸克-介子耦合模型被用来推导Λc+束缚态自旋子及交换介子的自能。该模型假设各个顶点的参数与之前研究基本的p¯+ p→Λ¯c-+Λc+反应时使用的参数一致。研究结果显示，在P？ANDA实验关注的反质子束动量下，0∘微分截面的OΛc+ 16超核态形成大小在几μb/ sr的范围内，显示了这种反应的可能性。" 本文是一篇开放获取的物理学文章，发表在《Physics Letters B》期刊上，作者来自印度萨哈核物理研究所和巴西克鲁塞罗多苏大学的理论与计算物理学实验室。文章经历了多次修订，最终于2017年4月27日在线发布。编辑为W.Haxton教授。关键词包括Λc+超核的生成、反质子-核碰撞、协变生产模型以及夸克-介子耦合模型。在文中，作者们主要关注了反质子与重核碰撞时如何产生含有奇异夸克的超核（即Λc+）。他们采用的协变模型是一种基于有效拉格朗日量的方法，允许在各种相对论框架下进行计算，以保持物理结果的不变性。Λc+超核的生成是通过反质子与目标核中的质子相互作用，通过t通道中的D0和D⁎0介子交换来实现的。这里的t通道交换是指交换粒子在相互作用过程中沿着与入射粒子运动方向垂直的动量空间中发生的。此外，文章还利用夸克-介子耦合模型来处理Λc+束缚态的自旋子以及在这一过程中涉及的介子的自能。这种模型能够描述夸克与介子之间的相互作用，从而帮助理解超核内部的结构和动力学。研究发现，对于P？ANDA实验所关注的反质子束动量条件，OΛc+ 16超核在0∘碰撞角度下的微分截面（表示单位立体角内的产生概率）处于几μb/ sr的范围。这表明在特定实验条件下，这种超核的生成是可探测的，并且对于理解强相互作用和奇异物质的性质具有重要意义。这项工作提供了关于反质子-核碰撞中产生Λc+超核的理论分析，为实验观测提供了理论基础，并为未来对奇异核物理的研究提供了有价值的参考。

Physics Letters B 770 (2017) 236–241

Contents lists available at ScienceDirect

Physics Letters B

www.elsevier.com/locate/physletb

Production of 

hypernuclei in antiproton–nucleus collisions

R. Shyam

a,∗

, K. Tsushima

Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700064, India

Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, Rua Galvão Bueno, 868, Liberdade 01506-000, São Paulo, SP, Brazil

a r t i c l e i n f o a b s t r a c t

Article history:

Received

23 December 2016

Received

in revised form 5 April 2017

Accepted

24 April 2017

Available

online 27 April 2017

Editor:

W. Haxton

Keywords:

Production

of 

hypernuclei

Antiproton–nucleus

collisions

Covariant

production model

Bound

charm-baryon spinors from

quark–meson coupling model

We investigate the production of charm-baryon hypernucleus



Oin the antiproton–

O collisions within

a fully covariant model that is based on an effective Lagrangian approach. The explicit



−



production

vertex is described by the t-channel D

and D

∗0

meson-exchanges in the initial collision of the incident

antiproton with one of the protons of the target nucleus. The 

bound state spinors as well as the

self-energies of the exchanged mesons employed in our calculations are derived from the quark–meson

coupling model. The parameters of various vertices are taken to be the same as those used in our previ-

ous

study of the elementary

p + p →



−

+ 

reaction. We ﬁnd that for antiproton beam momenta of

interest to the

PANDA experiment, the 0

◦

differential cross sections for the formation of



Ohypernu-

clear

states with simple particle–hole conﬁgurations, have magnitudes in the range of a few μb/sr.

(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP

The investigation of the production of heavy ﬂavor hadrons

consisting of a charm-quark is of considerable interest as it pro-

vides

an additional means for a better understanding of quantum

chromodynamics (QCD) (see, e.g., Refs. [1,2]). The future

PANDA

(“antiproton

annihilation at Darmstadt”) experiment at the under-

construction

antiproton and ion research facility (FAIR) in Darm-

stadt,

Germany, includes a rich program on the measurements of

the charm-meson and charm-baryon production in the antipro-

ton

(

p) collisions with proton and nuclei at the beam momenta

≤ 15 GeV/c [3]. The accurate knowledge of the charm-meson

(

and D

−

) production cross sections in these reactions, is

important because the charmonium states above the open charm

threshold will generally be identiﬁed by means of their decays to

DD channels if allowed [4,5].

Studies

of the production and spectroscopy of charm-baryons

(e.g. 

) are similarly interesting. In contrast to the mesons, there

can be more states of these systems as there are more possibilities

of orbital excitations due the presence of three quarks. At higher

beam

momenta at the

PANDA facility the yields of the channels

with charm-baryons exceed those of the charm-meson channels by

factors of 3–4, which is conﬁrmed by calculations of the produc-

tions



−



and

DD pairs in the

pp collisions in Refs. [6–9]. In

studies of the charm-baryon production in the

p induced reactions

on proton or nuclei the production of extra particles is not needed

Corresponding author .

E-mail

address: radhey.shyam@saha.ac.in (R. Shyam).

for the charm conservation, which reduces the threshold energy as

compared to, say, pp collisions. Investigations of the charm-baryon

(and also charm-meson) productions in the

p-nucleus collisions

explore the properties of charm-hadrons in the nuclear medium

and provide information about the charm hadron–nucleon (N) in-

teraction

in the nuclear medium [10–12].

The



–N interaction has come in focus after discoveries of

many exotic hadrons [e.g., X(3872), and Z(4430)] by the Belle

experiments [13,14]. These hadrons are considered to be either

the 4-quark bound states including the charm one or the com-

posite

states of two (or more) hadrons (see, e.g., Ref. [15] for a

review). There is no conclusive evidence for the existence of the

two-body bound states in the 

–N channel. It will critically de-

pend

on the nature of the 

–N interaction. Because performing

scattering experiments in this channel is not feasible for the time

being, alternative methods will have to be explored for determin-

ing

this interaction. Some effort has been made in this direction

in the lattice QCD calculations by the HAL QCD collaboration [16],

but their results are limited to pion masses around or in excess

of 600 MeV. Another viable alternative is to study 

hypernu-

clei

that can be produced in the

p induced reactions on nuclei at

the

PANDA facility . In the past the study of the  hypernuclear

states has provided important information about the –N interac-

tion

(see, e.g., the reviews [17–19]). Furthermore, in a theoretical

study of the -hypernuclei, it has been shown that the properties

of the states of such nuclei are strongly dependent on the nature

of the –N interaction [20].

http://dx.doi.org/10.1016/j.physletb.2017.04.057

0370-2693/

SCOAP

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