Exploring the electromagnetic properties of the Ξ cD sandΩ

2025-04-27 0 0 392.65KB 17 页 10玖币
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Exploring the electromagnetic properties of the Ξ(,)
c¯
D
sand ()
c¯
D
smolecular states
Fu-Lai Wang1,2,3,Si-Qiang Luo1,2,3,Hong-Yan Zhou1,2,Zhan-Wei Liu1,2,3,§and Xiang Liu1,2,3,4
1School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
2Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou 730000, China
3Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province,
and Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China
4Key Laboratory of Quantum Theory and Applications of MoE, Lanzhou University, Lanzhou 730000, China
This paper presents a systematic investigation of the electromagnetic properties of the hidden-charm molec-
ular pentaquarks within the constituent quark model. Specifically, it focuses on two types of pentaquarks: the
Ξ(,)
c¯
D
s-type pentaquarks with double strangeness and the ()
c¯
D
s-type pentaquarks with triple strangeness. The
study explores various electromagnetic properties, including the magnetic moments, the transition magnetic
moments, and the radiative decay behavior of these pentaquarks. To ensure realistic calculations, the S-Dwave
mixing eect and the coupled channel eect are taken into account. By examining the electromagnetic proper-
ties of the hidden-charm molecular pentaquarks with double and triple strangeness, this research contributes to
the deeper understanding of their spectroscopic behavior. These findings form a valuable addition to the ongoing
investigation into the broader spectrum of properties exhibited by the hidden-charm molecular pentaquarks.
I. INTRODUCTION
Since the observation of the charmoniumlike state X(3872)
in 2003, numerous new hadronic states have been experimen-
tally observed, leading to extensive discussions about their
properties. These eorts have significantly enriched our un-
derstanding of the hadron spectroscopy [122]. Moreover,
these studies have been valuable in deepening our understand-
ing of the nonperturbative behavior of the strong interactions.
Among the various assignments proposed for the observed
new hadronic states, the molecular state explanation has
gained popularity. Notably, in 2015, the LHCb Collabora-
tion observed two Pcstates [23] and subsequently reported
two substructures, namely Pc(4440) and Pc(4457) [24], corre-
sponding to the previously observed Pc(4450) [23]. Further-
more, they discovered a new state, Pc(4312), through a de-
tailed analysis of the ΛbJpK process [24]. The LHCb
experiment has provided strong experimental evidence for the
existence of the hidden-charm molecular pentaquarks of the
Σc¯
D()type [2531]. In subsequent years, LHCb reported
the evidence for Pcs(4459) [32] and observed PΛ
ψs(4338) [33].
These exciting experimental advancements have not only en-
riched the hidden-charm pentaquark family [3471,73?
80], but have also inspired theorists to investigate the hidden-
charm molecular pentaquarks of the Pcss(s)type [8184]. In
recent years, the Lanzhou group has conducted extensive stud-
ies on the mass spectra of the hidden-charm molecular pen-
taquarks with double and triple strangeness. Specifically, their
investigations have focused on the Ξ(,)
c¯
D()
s[81] and ()
c¯
D()
s
[82] interactions. These studies have provided valuable in-
sights into the properties and characteristics of these exotic
hadronic states.
wangfl2016@lzu.edu.cn
luosq15@lzu.edu.cn
zhouhy20@lzu.edu.cn
§liuzhanwei@lzu.edu.cn
xiangliu@lzu.edu.cn
Currently, the investigation of the properties of the hidden-
charm molecular pentaquarks remains a fascinating and sig-
nificant research topic in hadron physics. It oers valuable in-
sights for constructing a comprehensive family of the hidden-
charm molecular pentaquarks. The study of the electromag-
netic properties serves as an eective approach to unveil the
inner structures of hadrons. A notable example is the success-
ful application of the constituent quark model in describing
the magnetic moments of the decuplet and octet baryons [85
87], with corresponding experimental data available [88].
Given the importance of the electromagnetic properties,
it is crucial to investigate the electromagnetic characteristics
of the hidden-charm molecular pentaquarks. Some discus-
sions on the electromagnetic properties of the Σ()
c¯
D()-type
and Ξ(,)
c¯
D()-type hidden-charm molecular pentaquarks have
been conducted within the constituent quark model [8992].
These studies shed light on the inner structures of the dis-
cussed hidden-charm molecular pentaquarks. However, it is
important to note that the exploration of the electromagnetic
properties for the hidden-charm molecular pentaquarks is still
in its early stages. Thus, further eorts are required to obtain a
comprehensive understanding of the electromagnetic proper-
ties of various types of hidden-charm molecular pentaquarks.
In this study, our focus is on investigating the electromag-
netic properties of the hidden-charm molecular pentaquarks
with double strangeness, specifically the Ξ(,)
c¯
D
s-type pen-
taquarks, as well as those with triple strangeness, namely
the ()
c¯
D
s-type pentaquarks. These particular pentaquark
states were initially predicted in Refs. [81,82]. Within
the framework of the constituent quark model, we exam-
ine their magnetic moments, transition magnetic moments,
and radiative decay behavior. Our realistic calculations in-
corporate the eects of the S-Dwave mixing and coupled
channels. By undertaking this investigation, we aim to en-
hance our understanding of the electromagnetic properties
of the hidden-charm molecular pentaquarks with double and
triple strangeness, thereby contributing to the comprehensive
knowledge of these intriguing exotic hadrons [81,82].
The structure of this paper is as follows. In Sec. II,
arXiv:2210.02809v6 [hep-ph] 8 Aug 2023
2
we provide a detailed explanation of the methodology em-
ployed for calculating the electromagnetic properties of the
hadronic molecules. Additionally, we present the electromag-
netic properties of the Ξ(,)
c¯
D
smolecular states. In Sec. III, we
shift our focus to the electromagnetic properties of the ()
c¯
D
s
molecular states. Finally, we oer a concise summary of our
findings in Sec. IV.
II. THE ELECTROMAGNETIC PROPERTIES OF THE
Ξ(,)
c¯
D
sMOLECULES
In this section, we thoroughly investigate the electromag-
netic properties of two molecular states: the Ξ
c¯
D
sstate with
I(JP)=1/2(3/2) and the Ξ
c¯
D
sstate with I(JP)=1/2(5/2)
[81]. Specifically, we analyze their magnetic moments, transi-
tion magnetic moments, and radiative decay behavior. These
investigations yield valuable insights into the inner structures
of these states, oering significant information in this regard.
A. The magnetic moments and the transition magnetic
moments of the Ξ(,)
c¯
D
smolecules
In the context of the constituent quark model, the hadronic
magnetic moment encompasses two key components: the spin
magnetic moment and the orbital magnetic moment. Specifi-
cally, when considering the z-component of the spin magnetic
moment operator for a given hadron, denoted as ˆµspin
z, it can
be mathematically represented as follows [8587,89125]:
ˆµspin
z=X
j
ej
2Mj
ˆσz j,(1)
where ej,Mj, and ˆσz j denote the charge, the mass, and
the z-component of the Pauli spin operator of the jth con-
stituent of the hadron, respectively. When examining the
hadronic molecule comprised of a baryon and a meson, the
z-component of the orbital magnetic moment operator, de-
noted as ˆµorbital
z, can be expressed in the following manner
[8994,96,98,100,104,105,108,116]:
ˆµorbital
z=µL
bm ˆ
Lz
= Mm
Mb+Mm
eb
2Mb
+Mb
Mb+Mm
em
2Mm!ˆ
Lz,(2)
where the subscript bcorresponds to the baryon, while the
subscript mpertains to the meson. Furthermore, ˆ
Lzdenotes
the z-component of the orbital angular momentum operator
linking the baryon and the meson. In this study, the masses
of the S-wave charmed baryons and the S-wave charmed-
strange meson are extracted from the Particle Data Group [88]
for reference.
As extensively discussed in various references such as [85
87,89125], the magnetic moments of the hadrons (µH)
and the transition magnetic moments between the hadrons
(µHH) are frequently estimated by evaluating the expecta-
tion values of the z-component of the total magnetic moment
operator (ˆµz), which can be represented as
µH=JH,JH|ˆµz|JH,JH,(3)
µHH=JH,Jz|ˆµz|JH,JzJz=Min{JH,JH}.(4)
Here, ˆµz=ˆµspin
z+ˆµorbital
z, and H()stands for either the fun-
damental hadron or the compound hadron. In the realistic
calculations, the previous theoretical studies commonly em-
ploy the maximum value of the third component of the total
angular momentum quantum number for the hadron to deter-
mine the hadronic magnetic moment. Similarly, they consider
the maximum third component of the total angular momen-
tum quantum number of the lowest state of the total angu-
lar momentum to discuss the transition magnetic moment be-
tween the hadrons [8587,89125]. In our current study, we
adopt the same model and convention as previous theoretical
works for calculating the hadronic magnetic moments and the
hadronic transition magnetic moments [8587,89125]. In
order to provide a comprehensive analysis, it is necessary to
discuss the wave functions of the hadronic states under con-
sideration. These wave functions encompass various aspects,
including the color part, the flavor part, the spin part, and the
spatial part. Regarding the color wave function, it is straight-
forwardly represented by the constant value 1, as the color
aspect is typically treated uniformly in our context. On the
other hand, the flavor-spin wave function can be constructed
by taking into account the symmetry constraints imposed by
the system. Finally, the spatial wave function can be derived
by quantitatively studying the mass spectrum of the corre-
sponding hadron [92].
In the subsequent analysis, we delve into the magnetic mo-
ments and the transition magnetic moments of two specific
molecular states: the Ξ
c¯
D
smolecule with I(JP)=1/2(3/2)
and the Ξ
c¯
D
smolecular state with I(JP)=1/2(5/2). To ac-
complish this, we employ three distinct scenarios: the single-
channel analysis, the S-Dwave mixing analysis, and the cou-
pled channel analysis. These scenarios allow us to explore
the influence of the S-Dwave mixing eect and the coupled
channel eect on the magnetic moments and the transition
magnetic moments of the Ξ(,)
c¯
D
smolecular states. By em-
ploying the aforementioned procedures, we can elucidate the
respective contributions of these eects to the magnetic mo-
ments and the transition magnetic moments of the molecular
states under investigation.
1. The single channel analysis
Firstly, we investigate the magnetic moments and the tran-
sition magnetic moments of the Ξ
c¯
D
smolecular state with
I(JP)=1/2(3/2) and the Ξ
c¯
D
smolecule with I(JP)=
1/2(5/2), while considering only the S-wave component.
The flavor wave functions of these states, denoted as |I,I3,
can be expressed as [81]
1
2,1
2+=|Ξ(,)+
cD∗−
s,
1
2,1
2+=|Ξ(,)0
cD∗−
s,
3
where Iand I3represent the isospins and the isospin third
components of the Ξ(,)
c¯
D
ssystems, respectively. Further-
more, the spin wave functions |S,S3for these states can be
constructed using the following coupling scheme [81]
Ξ
c¯
D
s:|S,S3=X
SΞ
c,S¯
D
s
CS S 3
1
2SΞ
c,1S¯
D
s
1
2,SΞ
c+1,S¯
D
sE,
Ξ
c¯
D
s:|S,S3=X
SΞ
c,S¯
D
s
CS S 3
3
2SΞ
c,1S¯
D
s
3
2,SΞ
c+1,S¯
D
sE.
Here, Sand S3represent the total spins and the total spin
third components for the Ξ(,)
c¯
D
ssystems, respectively. The
Clebsch-Gordan coecient Ce f
ab,cd is utilized in the coupling
scheme. Additionally, SΞ
c,SΞ
c, and S¯
D
scorrespond to the
spin third components of Ξ
c,Ξ
c, and ¯
D
s, respectively.
With the aforementioned setup, we can now proceed to
calculate the magnetic moments of the Ξ
c¯
D
smolecule with
I(JP)=1/2(3/2) and the Ξ
c¯
D
smolecular state with I(JP)=
1/2(5/2), such as
µI3=1/2
Ξ
c¯
D
s|3/2=χ|1
2,1
2|1,1
Ξ+
cD∗−
s
ˆµz
χ|1
2,1
2|1,1
Ξ+
cD∗−
s
=µΞ+
c+µD∗−
s.(5)
Here, χs
frepresents the spin and flavor wave functions of the
hadron, while the superscript sindicates the spin wave func-
tion and the subscript fdenotes the flavor wave function. Fur-
thermore, in the context of the single channel analysis of the
hadronic magnetic moment, the overlap of the relevant spatial
wave function is 1. For brevity, this factor is omitted in the
above expression.
To determine the magnetic moments of the Ξ()
cbaryons
and the ¯
D
smeson, we employ the constituent quark model.
Initially, let us define the flavor and spin wave functions of
these particles. The flavor wave functions can be expressed as
follows:
Ξ()+
c:1
2(usc +suc),Ξ()0
c:1
2(dsc +sdc),D∗−
s: ¯cs,
while their corresponding spin wave functions |S,S3can be
expressed as
Ξ
c:
1
2,1
2+=1
6(2↑↑↓ − ↓↑↑ − ↑↓↑)
1
2,1
2+=1
6(↓↑↓ +↑↓↓ −2↓↓↑)
,
Ξ
c:
3
2,3
2+=↑↑↑
3
2,1
2+=1
3(↓↑↑ +↑↓↑ +↑↑↓)
3
2,1
2+=1
3(↓↓↑ +↑↓↓ +↓↑↓)
3
2,3
2+=↓↓↓
,
¯
D
s:
|1,1=↑↑
|1,0=1
2(↑↓ +↓↑)
|1,1=↓↓
.
Here, the notations and denote the third components of the
quark spins, with values of +1/2 and 1/2, respectively.
Based on the flavor and spin wave functions of the Ξ()
c
baryons and the ¯
D
smeson, we can proceed to calculate their
magnetic moments. As an example, let us deduce the mag-
netic moment of the Ξ+
cbaryon as follows:
µΞ+
c=*χ
1
6(2↑↑↓−↓↑↑−↑↓↑)
1
2(usc+suc)
ˆµz
χ
1
6(2↑↑↓−↓↑↑−↑↓↑)
1
2(usc+suc)+
=2
3µu+2
3µs1
3µc.(6)
In this study, we adopt the following definition for the mag-
netic magneton of the quark: µq=µ¯q=eq/2Mq, where
eqrepresents the charge of the quark and Mqdenotes the
constituent mass of the quark. Utilizing this definition, we
can derive the expressions for the magnetic moments of the
Ξ()
cbaryons and the ¯
D
smeson. For the numerical analy-
sis, we utilize the constituent quark masses Mu=0.336 GeV,
Md=0.336 GeV, Ms=0.450 GeV, and Mc=1.680 GeV
to quantitatively investigate the electromagnetic properties of
these discussed hadrons. These constituent quark masses are
sourced from Ref. [86] and are widely employed in studies
related to the magnetic moments of the hadronic molecular
states [90,92,98].
In Table I, we present the expressions and numerical re-
sults for the magnetic moments of the Ξ()
cbaryons and the
¯
D
smeson. Our obtained results align with those reported in
previous works [86,104,107,117,126129]. In this study,
the magnetic moments and the transition magnetic moments
of hadrons are expressed in units of the nuclear magneton
µN=e/2MPwith MP=0.938 GeV [88]. As shown in Ta-
ble I, the Ξ+
cand Ξ0
cbaryons exhibit distinct magnetic mo-
ments, while the magnetic moment of the Ξ+
cdiers from
that of the Ξ0
c. This discrepancy arises from the notable dif-
ference in the magnetic magnetons between the up quark and
the down quark, namely, µu=1.862 µNand µd=0.931 µN.
Moreover, the Ξ0
cand Ξ0
cexhibit approximately equal mag-
netic moments.
Based on our obtained magnetic moments of the Ξ()
c
baryons and the ¯
D
smeson, we can get the numerical re-
sults of the magnetic moments of the Ξ
c¯
D
smolecule with
I(JP)=1/2(3/2) and the Ξ
c¯
D
smolecular state with I(JP)=
1/2(5/2). In Table II, we present the expressions and numer-
ical results of the magnetic moments of the Ξ
c¯
D
smolecular
state with I(JP)=1/2(3/2) and the Ξ
c¯
D
smolecular state
with I(JP)=1/2(5/2) when performing the single channel
analysis.
As presented in Table II, the magnetic moments of the
Ξ
c¯
D
s|3/2molecule with I3=1/2, the Ξ
c¯
D
s|3/2molecule
with I3=1/2, the Ξ
c¯
D
s|5/2molecule with I3=1/2,
and the Ξ
c¯
D
s|5/2molecule with I3=1/2 are 0.414 µN,
2.275 µN, 0.472 µN, and 2.321 µN, respectively. Notably,
the magnetic moment of the Ξ
c¯
D
s|3/2molecular state can
be obtained as the sum of the magnetic moments of the Ξ
c
baryon and the ¯
D
smeson. Furthermore, the magnetic moment
of the Ξ+
csignificantly diers from that of the Ξ0
c, resulting
in a distinct magnetic moment for the Ξ
c¯
D
s|3/2molecule
4
TABLE I. The magnetic moments and the transition magnetic mo-
ments of the Ξ()
cbaryons and the ¯
D
smeson. The magnetic moment
and the transition magnetic moment are given in units of µN, where
µNdenotes the nuclear magneton. The expressions for the magnetic
moments and the transition magnetic moments are enclosed in the
square brackets in the second column.
Quantities Our work Other works
µΞ+
c0.654 h2
3µu+2
3µs1
3µci0.65 [126], 0.67 [127]
µΞ0
c1.208 h2
3µd+2
3µs1
3µci1.20 [128], 1.20 [127]
µΞ+
c1.539 µu+µs+µc1.51 [129], 1.59 [104]
µΞ0
c1.254 µd+µs+µc1.20 [117], 1.18 [107]
µD∗−
s1.067 µc+µs1.00 [117], 1.08 [127]
µΞ+
cΞ+
c0.199 h2
3(µu+µs2µc)i0.17 [86], 0.16 [130]
µΞ0
cΞ0
c1.117 h2
3(µd+µs2µc)i1.07 [117], 1.03 [117]
TABLE II. The expressions and numerical results of the magnetic
moments of the Ξ
c¯
D
smolecular state with I(JP)=1/2(3/2) and
the Ξ
c¯
D
smolecular state with I(JP)=1/2(5/2) when only the S-
wave component is considered.
Physical quantities Expressions Values
µI3=1/2
Ξ
c¯
D
s|3/2µΞ+
c+µD∗−
s0.414 µN
µI3=1/2
Ξ
c¯
D
s|3/2µΞ0
c+µD∗−
s2.275 µN
µI3=1/2
Ξ
c¯
D
s|5/2µΞ+
c+µD∗−
s0.472 µN
µI3=1/2
Ξ
c¯
D
s|5/2µΞ0
c+µD∗−
s2.321 µN
with I3=1/2 compared to that with I3=1/2. Similarly, the
Ξ
c¯
D
s|5/2molecular state exhibits dierent magnetic mo-
ments for various I3quantum numbers. In addition, the mag-
netic moments of the Ξ
c¯
D
s|3/2molecule with I3=1/2
and the Ξ
c¯
D
s|5/2molecule with I3=1/2 are nearly the
same, owing to the close magnetic moments of the Ξ0
cand
Ξ0
c.
In addition to investigating the magnetic moments, we also
examine the transition magnetic moments between the Ξ
c¯
D
s
molecular state with I(JP)=1/2(3/2) and the Ξ
c¯
D
smolec-
ular state with I(JP)=1/2(5/2). The transition magnetic
moment between these two states can be determined using the
following expression:
µI3=1/2
Ξ
c¯
D
s|5/2⟩→Ξ
c¯
D
s|3/2
=χ|1
2,1
2|1,1
Ξ+
cD∗−
s
ˆµz
χ2
5|3
2,3
2|1,0+3
5|3
2,1
2|1,1
Ξ+
cD∗−
s+
=r3
5µΞ+
cΞ+
c.(7)
Hence, the transition magnetic moment for the Ξ
c¯
D
s|5/2⟩ →
Ξ
c¯
D
s|3/2γprocess can be connected to that of the Ξ
c
Ξ
cγprocess. It should be noted that the spatial wave func-
tions of the initial and final states may influence the transition
magnetic moment, and this aspect will be addressed in the
subsequent subsection. Next, we proceed to estimate the tran-
sition magnetic moment for the Ξ+
cΞ+
cγprocess, which
can be obtained from the expression
µΞ+
cΞ+
c=*χ
1
3(↓↓↑+↑↓↓+↓↑↓)
1
2(usc+suc)
ˆµz
χ
1
6(2↑↑↓−↓↑↑−↑↓↑)
1
2(usc+suc)+
=2
3(µu+µs2µc).(8)
Table Ipresents the expressions and numerical values of the
transition magnetic moments for the Ξ+
cΞ+
cγand Ξ0
c
Ξ0
cγprocesses. The obtained results from our analysis are in
good agreement with the theoretical predictions reported in
Refs. [86,117,130].
Based on the calculated transition magnetic moments for
the Ξ+
cΞ+
cγand Ξ0
cΞ0
cγprocesses, we can determine
the values of the transition magnetic moments between the
Ξ
c¯
D
smolecule with I(JP)=1/2(3/2) and the Ξ
c¯
D
smolec-
ular state with I(JP)=1/2(5/2). Specifically, we find that
µI3=1/2
Ξ
c¯
D
s|5/2⟩→Ξ
c¯
D
s|3/2=0.154 µN,
µI3=1/2
Ξ
c¯
D
s|5/2⟩→Ξ
c¯
D
s|3/2=0.866 µN.
It should be noted that the magnitude of the transition mag-
netic moment for the Ξ0
cΞ0
cprocess is significantly larger
than that for the Ξ+
cΞ+
cprocess [117,130]. Consequently,
the absolute value of µΞ
c¯
D
s|5/2⟩→Ξ
c¯
D
s|3/2with I3=1/2 is
considerably greater than that with I3=1/2.
2. The S -D wave mixing analysis
And then, we conduct further investigations on the mag-
netic moments and the transition magnetic moments of the
Ξ
c¯
D
smolecular state with I(JP)=1/2(3/2) and the Ξ
c¯
D
s
molecule with I(JP)=1/2(5/2) by considering the addi-
tional contribution from the D-wave channels. Our calcula-
tions encompass the following S-wave and D-wave channels
for the Ξ
c¯
D
smolecular state with I(JP)=1/2(3/2) and the
Ξ
c¯
D
smolecular state with I(JP)=1/2(5/2) [81]
Ξ
c¯
D
s|3/2:|4S3/2,|2D3/2,|4D3/2,
Ξ
c¯
D
s|5/2:|6S5/2,|2D5/2,|4D5/2,|6D5/2.
Here, we adopt the notation |2S+1LJto denote the spin S, or-
bital angular momentum L, and total angular momentum Jof
the molecular state under consideration.
By considering the influence of the S-Dwave mixing ef-
fect, we can derive the magnetic moment and the transition
magnetic moment of the molecular states through the follow-
ing deductions
X
i,j
µAi→AjϕAj|ϕAi,(9)
X
i,j
µBi→AjϕAj|ϕBi,(10)
摘要:

ExploringtheelectromagneticpropertiesoftheΞ(′,∗)c¯D∗sandΩ(∗)c¯D∗smolecularstatesFu-LaiWang1,2,3,∗Si-QiangLuo1,2,3,†Hong-YanZhou1,2,‡Zhan-WeiLiu1,2,3,§andXiangLiu1,2,3,4¶1SchoolofPhysicalScienceandTechnology,LanzhouUniversity,Lanzhou730000,China2ResearchCenterforHadronandCSRPhysics,LanzhouUniversitya...

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