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1.
We argue that the mass, production, total decay width, and decay pattern of the η
2(1870) do not appear to contradict with the picture of it as being the conventional 2 1
D
2
q[`( q)]q\bar{q}
state. The possibility of the η
2(1870) being a mixture of the conventional
q[`( q)]q\bar{q}
and a hybrid is also discussed. 相似文献
2.
In this article, we assume that there exist scalar D*[`( D)] *{D}^{\ast}{\bar {D}}^{\ast}, Ds*[`( D)] s*{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B*[`( B)] *{B}^{\ast}{\bar {B}}^{\ast} and Bs*[`( B)] s*{B}_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about
(250–500) MeV above the corresponding D
*–[`( D)] *{\bar{D}}^{\ast}, D
s
*–[`( D)] s*{\bar {D}}_{s}^{\ast}, B
*–[`( B)] *{\bar{B}}^{\ast} and B
s
*–[`( B)] s*{\bar {B}}_{s}^{\ast} thresholds, the Y(4140) is unlikely a scalar Ds*[`( D)] s*{D}_{s}^{\ast}{\bar{D}}_{s}^{\ast} molecular state. The scalar D*[`( D)] *D^{\ast}{\bar{D}}^{\ast}, Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}, B*[`( B)] *B^{\ast}{\bar{B}}^{\ast} and Bs*[`( B)] s*B_{s}^{\ast}{\bar{B}}_{s}^{\ast} molecular states maybe not exist, while the scalar D¢ *[`( D)] ¢*{D'}^{\ast}{\bar{D}}^{\prime\ast}, Ds¢*[`( D)] s¢*{D}_{s}^{\prime\ast}{\bar{D}}_{s}^{\prime\ast}, B¢*[`( B)] ¢*{B}^{\prime\ast}{\bar{B}}^{\prime\ast} and Bs¢*[`( B)] s¢*{B}_{s}^{\prime\ast}{\bar{B}}_{s}^{\prime\ast} molecular states maybe exist. 相似文献
3.
We study meson-meson interactions using an extended q
2
[`( q)] 2 ( g)\bar q^2 (g) basis that allows calculating coupling of an ordinary meson-meson system to a hybrid-hybrid one. We use a potential model
matrix in this extended basis which at quark level is known to provide a good fit to numerical simulations of a q
2
[`( q)] 2\bar q^2 system in pure gluonic theory for static quarks in a selection of geometries. We use a combination of resonating group method
formalism and Born approximation to include the quark motion using wave functions of a q[`( q)]q\bar q potential within a cluster. This potential is taken to be quadratic for ground states and has an additional smeared $\frac{1}
{r}$\frac{1}
{r} (Gaussian) for the matrix elements between hybrid mesons. For the parameters of this potential, we use values chosen to 1)
minimize the error resulting from our use of a quadratic potential and 2) best fit the lattice data for differences of Σ
g
and Π
u
configurations of the gluonic field between a quark and an antiquark. At the quark (static) level, including the gluonic
excitations, was noted to partially replace the need for introducing many-body terms in a multiquark potential. We study how
successful such a replacement is at the (dynamical) hadronic level of relevance to actual hard experiments. Thus we study
the effects of both gluonic excitations and many-body terms on mesonic transition amplitudes and the energy shifts resulting
from the second-order perturbation theory ( i.e. from the respective hadron loops). The study suggests introducing both energy and orbital excitations in wave functions of
scalar mesons that are modelled as meson-meson molecules or are supposed to have a meson-meson component in their wave functions. 相似文献
4.
In this paper we consider a quark-antiquark ( q[`( q)]q\bar{q}) pair which can be interpreted as a meson in N=4{\mathcal{N}}=4 SYM thermal plasma. We assume that the string moves at speed v and rotates around its center of mass simultaneously. By using the AdS/CFT correspondence, we obtain the momentum densities
of the rotating string and determine its motion for small angular velocities. Then in general case, we calculate the screening
length of q[`( q)]q\bar{q} pair numerically and show that its velocity dependance is in consistent with the well known formula L
s
T∼(1− v
2) 1/4 in the literature. 相似文献
5.
We study the properties of D and [`( D)] \bar{{D}} mesons in hot isospin asymmetric strange hadronic matter, arising due to their interactions with the hadrons in the hyperonic
medium. The interactions of D and [`( D)] \bar{{D}} mesons with these light hadrons are derived by generalizing the chiral SU(3) model used for the study of hyperonic matter to SU(4). The nucleons, hyperons, the scalar isoscalar meson, σ and the scalar-isovector meson, d \delta as modified in the strange hadronic matter, modify the masses of D and [`( D)] \bar{{D}} mesons. It is found that, as compared to the [`( D)] \bar{{D}} mesons ([`( D0)] \bar{{D^0}}, D
−), the properties of the D mesons ( D
0, D
+) are more sensitive to the isospin asymmetry at high densities. On the other hand, the effects of strangeness fraction are
found to be more dominant for the [`( D)] \bar{{D}} mesons as compared to the D mesons and these modifications are observed to be particularly appreciable at high densities. We also study the mass modifications
of the charmonium states J/ ψ, ψ(3686) and ψ(3770) in the isospin asymmetric strange hadronic matter at finite temperatures and investigate the possibility of the decay
of the charmonium states into D
[`( D)] \bar{{D}} pairs in the hot hadronic medium. The mass modifications of these charmonium states arise due to their interaction with the
gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD
within the effective chiral model. The effects of finite quark masses are taken into account in the trace of the energy momentum
tensor in QCD, while investigating the medium modification of the charmonium masses through the modification of the gluon
condensate in the medium. We also compute the partial decay widths of the charmonium states to the D
[`( D)] \bar{{D}} pairs in the hadronic medium. The strong dependence on density of the in-medium properties of the D, [`( D)] \bar{{D}} and the charmonium states, as well as the partial decay widths of charmonium states to D
[`( D)] \bar{{D}} pairs, found in the present investigation, will be of direct relevance in observables like open charm enhancement as well
as J/ ψ suppression in the compressed baryonic matter (CBM) experiments at the future Facility for Antiproton and Ion Research, GSI,
where the baryonic matter at high densities is planned to be produced. 相似文献
6.
In this paper, we consider a rotating heavy quark-antiquark ( q[`( q)]q\bar{q}) pair in a N=4{\mathcal{N}}=4 SYM thermal plasma. We assume that q[`( q)]q\bar{q} center of mass moves at the speed v and furthermore they rotate around the center of mass. We use the AdS/CFT correspondence and consider the effect of external
electromagnetic field on the motion of the rotating meson. Then we calculate the jet-quenching parameter corresponding to
the rotating meson in the constant electric field. 相似文献
7.
A model-independent analysis of anomalous gauge coupling constants of W
± bosons is presented and the corresponding restrictions on them and on the electromagnetic characteristics of W
± bosons following from the experiments on measuring the e+ e- ? W+ W- ? ( e | / |
m, [`(v)] ) ?( q,[`(q)] ) {e^{+} }{e^{-} } \to {W^{+} }{W^{-} } \to \left( {{{e} \left/ {{\mu, \bar{v}}} \right.}} \right) \oplus \left( {q,\bar{q}} \right) process on the e
+
e
− International Linear Collider are obtained. The method of obtaining the model-independent restrictions on the anomalous gauge
constants is based on the use of the polarization scattering cross sections for different initial and final polarization states. 相似文献
8.
By introducing the mixing of scalar mesons in the chiral SU(3) quark model, we dynamically investigate the baryon-baryon interaction. The hyperon-nucleon and nucleon-nucleon interactions
are studied by solving the resonating group method (RGM) equation in a coupled-channel calculation. In our present work, the
experimental lightest pseudoscalar p \pi, K,h \eta,h ¢ \eta^{{\prime}}_{} mesons correspond exactly to the chiral nonet pseudoscalar fields p \pi, K,h \eta,h ¢ \eta^{{\prime}}_{} in the chiral SU(3) quark model. The h \eta,h ¢ \eta^{{\prime}}_{} mesons are considered as the mixing of singlet and octet mesons, and the mixing angle q ps \theta_{{ps}}^{} is taken to be -23 ° . For scalar nonet mesons, we suppose that there exists a correspondence between the experimental lightest scalar f
0(600) , k \kappa , a
0(980) , f
0(980) mesons and the theoretical scalar nonet s \sigma , k \kappa , s ¢ \sigma^{{\prime}}_{} , e \epsilon fields in the chiral SU(3) quark model. For scalar mesons, we consider two different mixing cases: one is the ideal mixing and another is the q s \theta_{s}^{} = 19 ° mixing. The masses of the s ¢ \sigma^{{\prime}}_{} and e \epsilon mesons are taken to be 980MeV, which are just the masses of the experimental a
0(980) , f
0(980) mesons. The mass of the s \sigma meson is an adjustable parameter and is decided by fitting the binding energy of the deuteron, the masses of 560MeV and 644MeV
are obtained for the ideal mixing and the q s \theta_{s}^{} = 19 ° mixing, respectively. We find that, in order to reasonably describe the YN interactions, the mass of the k \kappa meson is near 780MeV for the ideal mixing. However, we must enhance the mass of the k \kappa meson for the q s \theta_{s}^{} = 19 ° mixing, the 1050MeV is favorably used in the present work. The experimental s \sigma and k \kappa scalar mesons are very strange, both have larger widths. Hence, no matter what kind of mixing is considered, all the masses
of scalar mesons we used in the present work seem to be consistent with the present PDG information. 相似文献
9.
The interpretation of Y(4140) as a D*s[`( D)] *sD^{*}_{s}\bar{D}^{*}_{s} molecule is studied dynamically in the one boson exchange approach, where σ, η and φ exchange are included. Ten allowed D*s[`( D)] *sD^{*}_{s}\bar{D}^{*}_{s} states with low spin parity are considered, and we find that the J
PC
=0 ++, 1 +−, 0 −+, 2 ++ and 1 −−
D*s[`( D)] *sD^{*}_{s}\bar{D}^{*}_{s} configurations are most tightly bound. We suggest that the most favorable quantum numbers are J
PC
=0 ++ for Y(4140) as a D*s[`( D)] *sD^{*}_{s}\bar{D}^{*}_{s} molecule; however, J
PC
=0 −+ and 2 ++ cannot be excluded. We propose to search for the 1 +− and 1 −− partners in the J/ ψ
η and J/ ψ
η′ final states, which is an important test of the molecular hypothesis of Y(4140) and the reasonability of our model. The 0 ++
B*s[`( B)] *sB^{*}_{s}\bar{B}^{*}_{s} molecule should be deeply bound; experimental search in the ϒ(1 S) φ channel at Tevatron and LHC is suggested. 相似文献
10.
In this article, we assume that there exists a scalar
Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}
molecular state in the J/ ψ
φ invariant mass distribution, and we study its mass using the QCD sum rules. The predictions depend heavily on the two criteria
(pole dominance and convergence of the operator product expansion) of the QCD sum rules. The value of the mass is about
MDs*[`(D)]s*=(4.43±0.16)M_{D_{s}^{\ast}{\bar{D}}_{s}^{\ast}}=(4.43\pm0.16)
GeV, which is inconsistent with the experimental data. The
Ds*[`( D)] s*D_{s}^{\ast}{\bar{D}}_{s}^{\ast}
is probably a virtual state and is not related to the meson Y(4140). Another possibility, such as a hybrid charmonium, is not excluded. 相似文献
11.
The polarizations of Λ and
[`\varLambda]{\bar{\varLambda}} are thought to retain memories of the spins of their parent s quarks and [`( s)]{\bar{s}} antiquarks, and are readily measurable via the angular distributions of their daughter protons and antiprotons. Correlations between the spins of Λ and
[`\varLambda]{\bar{\varLambda}} produced at low relative momenta may therefore be used to probe the spin states of s [`( s)]s {\bar{s}} pairs produced during hadronization. We consider the possibilities that they are produced in a 3P 0 state, as might result from fluctuations in the magnitude of á[`( s)] s ?\langle {\bar{s}} s \rangle, a 1S 0 state, as might result from chiral fluctuations, or a 3S 1 or other spin state, as might result from production by a quark–antiquark or gluon pair. We provide templates for the p [`( p)]p {\bar{p}} angular correlations that would be expected in each of these cases, and discuss how they might be used to distinguish s [`( s)]s {\bar{s}} production mechanisms in pp and heavy-ion collisions. 相似文献
12.
Singlet ( X
1Σ +) and triplet ( a
3Σ +) potentials of interaction of two potassium atoms residing in the ground state (4 s
2
S
1/2) are presented. Based on the given interaction potentials, the complex cross sections of spin exchange q = [`( q)] + i[`([`( q)])]q = \bar q + i\overline{\overline q} for the system under investigation are calculated. Obtained dependences of the real and imaginary parts of the spin-exchange
cross section on temperature allow one to obtain information both on the broadening of a magnetic resonance line of K atoms
and on the frequency shift of the magnetic resonance during collision. 相似文献
13.
A gauge model featuring a chiral color symmetry of quarks was considered, and possible manifestations of this symmetry in
proton-antiproton and proton-proton collisions at the Tevatron and LHC energies were studied. The cross section s t[`(t)]\sigma _{t\bar t} for the production of t[`( t)]t\bar t quark pairs at the Tevatron and the forward-backward asymmetry AFBp[`(p)]A_{FB}^{p\bar p} in this process were calculated and analyzed with allowance for the contributions of the G′-boson predicted by the chiral color symmetry of quarks, the G′-boson mass m
G′ and the mixing angle θ
G
being treated as free parameters of the model. Limits on m
G′ versus θ
G
were studied on the basis of data from the Tevatron on s t[`(t)]\sigma _{t\bar t} and AFBp[`(p)]A_{FB}^{p\bar p}, and the region compatible with these data within one standard deviation was found in the m
G′- θ
G
plane. The region of m
G′-mass values that is appropriate for observing the G′-boson at LHC is discussed. 相似文献
14.
The use is suggested of a laser-accelerated dense electron sheet with
an energy of ( E=[(g)\tilde] mc2E=\tilde{\gamma} mc^2) as a relativistic mirror to reflect coherently a second
laser with photon energy ħω, generating by the Doppler boost
high-energy γ photons with $
\hbar \omega ' = 4\tilde \gamma ^2 \hbar \omega
$
\hbar \omega ' = 4\tilde \gamma ^2 \hbar \omega
and
short duration [A. Einstein, Annalen der Physik 17, 891 (1905); D. Habs et al., Appl. Phys. B 93, 349 (2008)]. Two of these counter-propagating
γ beams are focused by the parabolically shaped electron sheets into the
interaction region with small, close to diffraction-limited, spot size.
Comparing the new nγ-mγ collider with former proposed
γγ collider schemes we achieve the conversion of many
photon-pairs in a small space-time volume to matter-antimatter particles,
while in the other discussed setups only two isolated, much more
high-energetic photons will be converted, reaching in the
new approach much higher energy densities and temperatures.
With a γ-field strength somewhat below the Schwinger limit we can
reach this complete conversion of the γ bunch energy into
e +e - or quark-antiquark q[`( q)]q\bar{q}-plasmas.
For a Bose-Einstein condensate (BEC) [A. Einstein, Physikalisch-mathematische Klasse (Berlin) 22, 261 (1924); A. Einstein, Physikalisch-mathematische Klasse (Berlin) 22, 3 (1925); A. Griffin, D.W. Snoke, S. Stringari, Bose-Einstein Condensation (Cambridge University Press, 1995)] final state or for the Cooper pair ground state at higher densities [A.J. Leggett, Quantum Liquids, Oxford Graduate Texts (Oxford University Press, 2006)] the strong induced transition
into this coherent state is of special interest for single-cycle γ
pulses. Due to annihilation these cold coherent states are very
short-lived. For γ beams with photon energies
of 1–10 keV the rather cold e +e --plasma or
e +e --BEC expands to a cold dense aggregate of positronium (Ps)
atoms, where the production of Ps molecules is discussed.
For photon energies of 1–10 MeV we discuss the production of
a cold induced π 0-BEC followed by the formation of molecules.
For the direct population of higher q[`( q)]q\bar{q} densities we can study
condensates of color-neutral mesons with enhanced population.
For a γγ collider with several-cycle laser pulses
the following cycles heat up the fermion-antifermion
f[`( f)]f\bar{f} system to a certain temperature.
Thus we can reach high energy densities and temperatures of an e +e -γ
plasma, where the production of hadrons in general or the quark-gluon
phase transition can be observed. Within the long-term goal of very
high photon energies of about 1 GeV in the nγ-mγ-collider,
even the electro-weak phase transition or SUSY phase transition
could be reached. 相似文献
15.
Cross sections of scalar mesons f
0(980), a
0(980), and σ(600) production by colliding electron-positron beams are calculated. Two-photon decay widths of scalar mesons
obtained in the Nambu-Jona-Lasinio model are used with quark and meson loops taken into account. 相似文献
16.
The light flavor antiquark distributions of the nucleon sea are calculated in the effective chiral quark model and compared
with experimental results. The contributions of the flavor-symmetric sea-quark distributions and the nuclear EMC effect are
taken into account to obtain the ratio of Drell–Yan cross sections σ
pD/2 σ
pp, which can match well with the results measured in the FermiLab E866/NuSea experiment. The calculated results also match
the [`( d)]( x)-[`( u)]( x)\bar{d}(x)-\bar{u}(x) measured in different experiments, but unmatch the behavior of [`( d)]( x)/[`( u)]( x)\bar{d}(x)/\bar{u}(x) derived indirectly from the measurable quantity σ
pD/2 σ
pp by the FermiLab E866/NuSea Collaboration at large x. We suggest to measure again [`( d)]( x)/[`( u)]( x)\bar{d}(x)/\bar{u}(x) at large x from precision experiments with careful treatment of the experimental data. We also propose an alternative procedure for
experimental data treatment. 相似文献
17.
In this article, we take the point of view that the scalar mesons f0(980) and a0(980) are the diquark-antidiquark states
, and we devote our attention to the determination of their masses in the framework of the QCD sum rule approach with the interpolating currents constructed from scalar-scalar type and pseudoscalar-pseudoscalar type diquark pairs respectively. The numerical results indicate that the scalar mesons f0(980) and a0(980) may have two possible diquark-antidiquark substructures.Received: 27 January 2005, Revised: 22 March 2005, Published online: 31 May 2005PACS:
12.38.Lg; 13.25.Jx; 14.40.Cs 相似文献
18.
In this article, we study the mass spectrum of the baryon-antibaryon bound states p
[`( p)] \bar{{p}} , S \Sigma
[`(S)] \bar{{\Sigma}} , X \Xi
[`(X)] \bar{{\Xi}} , L \Lambda
[`(L)] \bar{{\Lambda}} , p
[`( N)] \bar{{N}}(1440) , S \Sigma
[`(S)] \bar{{\Sigma}}(1660) , X \Xi
[`(X)] ¢ \bar{{\Xi}}^{{\prime}}_{} and L \Lambda
[`(L)] \bar{{\Lambda}}(1600) with the Bethe-Salpeter equation. The numerical results indicate that the p
[`( p)] \bar{{p}} , S \Sigma
[`(S)] \bar{{\Sigma}} , X \Xi
[`(X)] \bar{{\Xi}} , p
[`( N)] \bar{{N}}(1440) , S \Sigma
[`(S)] \bar{{\Sigma}}(1660) , X \Xi
[`(X)] ¢ \bar{{\Xi}}^{{\prime}}_{} bound states maybe exist, and the new resonances X(1835) and X(2370) can be tentatively identified as the p
[`( p)] \bar{{p}} and p
[`( N)] \bar{{N}}(1440) (or N(1400)[`( p)] \bar{{p}} bound states, respectively, with some gluon constituents, and the new resonance X(2120) may be a pseudoscalar glueball. On the other hand, the Regge trajectory favors identifying the X(1835) , X(2120) and X(2370) as the excited h ¢ \eta^{{\prime}}_{}(958) mesons with the radial quantum numbers n = 3 , 4 and 5, respectively. 相似文献
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