共查询到20条相似文献,搜索用时 250 毫秒
1.
S. R. Gevorkyan A. N. Sissakian A. V. Tarasov H. T. Torosyan O. O. Voskresenskaya 《Physics of Atomic Nuclei》2010,73(6):961-964
The final-state interaction of pions in K
e4 decay allows to obtain the value of the isospin and angular-momentum-zero ππ scattering length a
00.We take into account the electromagnetic interaction of pions and isospin-symmetry-breaking effects caused by different masses
of neutral and charged pions and estimate the impact of these effects on the procedure of scattering-length extraction from
K
e4 decays. 相似文献
2.
K. Ghorbani M. M. Yazdanpanah A. Mirjalili 《The European Physical Journal C - Particles and Fields》2011,71(6):1671
We calculate the scalar semileptonic kaon decay in finite volume at the momentum transfer t
m
=(m
K
−m
π
)2, using chiral perturbation theory. At first we obtain the hadronic matrix element to be calculated in finite volume. We then
evaluate the finite size effects for two volumes with L=1.83 fm and L=2.73 fm and find that the difference between the finite volume corrections of the two volumes are larger than the difference
as quoted in Boyle et al. (Phys. Rev. Lett. 100:141601, 2008). It appears then that the pion masses used for the scalar form factor in ChPT are large which result in large finite volume
corrections. If appropriate values for pion mass are used, we believe that the finite size effects estimated in this paper
can be useful for lattice data to extrapolate at large lattice size. 相似文献
3.
G. Colangelo J. Gasser A. Rusetsky 《The European Physical Journal C - Particles and Fields》2009,59(4):777-793
Data on K
e4 decays allow one to extract experimental information on the elastic π
π scattering amplitude near threshold, and to confront the outcome of the analysis with predictions made in the framework of
QCD. These predictions concern an isospin symmetric world, while experiments are carried out in the real world, where isospin-breaking
effects—generated by electromagnetic interactions and by the mass difference of the up and down quarks—are always present.
We discuss the corrections required to account for these, so that a meaningful comparison with the predictions becomes possible.
In particular, we note that there is a spectacular isospin-breaking effect in K
e4 decays. Once it is taken into account, the previous discrepancy between NA48/2 data on K
e4 decays and the prediction of π
π scattering lengths disappears. 相似文献
4.
M. van Leeuwen 《The European Physical Journal C - Particles and Fields》2009,61(4):569-574
We present selected recent results of multi-hadron correlation measurements in azimuth and pseudorapidity at intermediate
and high p
T
in Au+Au collisions at
, from the STAR experiment at RHIC. At intermediate p
T
, measurements are presented that attempt to determine the origin of the associated near-side (small Δφ) yield at large pseudo-rapidity difference Δη that is found to be present in heavy ion collisions. In addition, results are reported on new multi-hadron correlation measures
at high-p
T
that use di-hadron triggers and multi-hadron cluster triggers with the goal to constrain the underlying jet kinematics better
than in the existing measurements of inclusive spectra and di-hadron correlations. 相似文献
5.
6.
U. Aglietti F. Di Lodovico G. Ferrera G. Ricciardi 《The European Physical Journal C - Particles and Fields》2009,59(4):831-840
By analyzing B→X
u
ℓ
ν
ℓ
spectra with a model based on soft-gluon resummation and an analytic time-like QCD coupling, we obtain
where the first and the second error refer to experimental and theoretical error, respectively. This model successfully describes
the accurate experimental data in beauty fragmentation, which has similar soft-gluon effects. The |V
ub
| value is obtained from the available measured semileptonic branching fractions in limited regions of the phase space. The
distributions in the lepton energy E
ℓ
, the hadron invariant mass m
X
, the light-cone momentum
, together with the double distributions in (m
X
,q
2) and (E
ℓ
,s
hmax ), are used to select the phase-space regions. q
2 is the dilepton squared momentum and s
hmax is the maximal m
X
2 at fixed q
2 and E
ℓ
. The |V
ub
| value obtained is in complete agreement with the value coming from exclusive B decays and from an over-all fit to the standard model parameters. We show that the slight disagreement (up to +2σ) with respect to previous inclusive measurements is not related to different choices for the b (and c) masses, but to a different modeling of the threshold (Sudakov) region. 相似文献
7.
I. V. Ovchinnikov T. A. Ivanova A. N. Turanov R. R. Garipov 《Physics of the Solid State》2009,51(10):2058-2063
Significant differences in the manifestation of spin-crossover properties of the mesogen compounds [FeL
2]X with oxysalicylidene-N′-ethyl-N-ethylenediamine ligands L and anions X = PF6− and SCH− have been found by means of electron paramagnetic resonance. The electron paramagnetic resonance data and the quantum-chemical
calculation within the density functional theory enables us to establish that the observed specific features are associated
with the incorporation of the SCH− ion into the first coordination sphere of the Fe(III) ion. The role of the transition of the material to the liquid-state
phase in the formation of a low-dimensional (two-dimensional) structure with stronger intermolecular interactions has been
revealed. 相似文献
8.
B. P. Lavrov 《Russian Journal of Physical Chemistry B, Focus on Physics》2012,6(2):239-248
A statistical analysis of all the available data on the wave numbers of spectral lines related to triplet-triplet electronic-vibrational-rotational
(rovibronic) radiation transitions into the H2 molecule (1sσ2sσ) a
3Σ
g
+ electronic state was performed for the first time. This allowed us to check and refine the controversial identification of
several spectral lines. Optimum rovibronic term values were found for 15 electronic states, including the (4pσ)f
3Σ
u
+, (4pπ)k
3Π
u
+, and (4pπ)k
3Π
u
− states studied in this work. The ratios between the oscillator strengths of R- and P-branch lines with common upper levels (branching coefficients) for the f
3Σ
u
+ → a
3Σ
g
+ and k
3Π
u
+ → a
3Σ
g
+ systems of H2 molecule bands were measured for the first time. Substantial deviations of the measured branching coefficients from the corresponding
ratios between the Henl-London factors were observed. The deviations monotonically increased as the rotational quantum number
N grew, which, in combination with substantial Λ-doubling in the k
3Π
u
state, was evidence of an important role played by electronicrotational interaction in the 4pσ3Σ
u
+ and 4pπ3Π
u
+ adiabatic electronic states. A strong correlation was observed between the N dependences of branching coefficients for transitions from the mutually perturbed f
3Σ
u
+ and k
3Π
u
+ electronic states. The results of this work show that the measured branching coefficients are a much more sensitive and capacious
channel of information about perturbation effects than rovibronic term values. 相似文献
9.
A comparative investigation of the magnetic properties of amorphous nanogranular composites (Co41Fe39B20)
x
(SiO
n
)100 − x
and (Co86Nb12Ta2)
x
(SiO
n
)100 − x
has been performed in the subpercolation region at temperatures in the range 4.2–300 K. The thermomagnetic dependences in
the range 4.2–300 K and the processes of magnetization reversal and remanent magnetization relaxation at liquid-helium temperatures
have been studied. It has been established that the average anisotropy constants of amorphous nanograins are equal to 3.6–7.0
kJ/m3 for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites and 5–8 kJ/m3 for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites. The fundamental differences in the concentration dependences of the anisotropy constant K
eff and the coercive force H
C
have been revealed for the two systems under investigation. It has been demonstrated that, as the concentration of the metal
phase increases, the quantities K
eff and H
C
increase for the (Co86Nb12Ta2)
x
(SiO
n
)100 − x
composites and decrease for the (Co41Fe39B20)
x
(SiO
n
)100 − x
composites. 相似文献
10.
New experimental data on fluctuations in the multiplicities of negatively charged particles in interactions of light nuclei
(p, d, 4He, 12C) with carbon nuclei at a momentum of 4.2 A GeV/c in 4π geometry are reported. The data indicate a behavior similar to that earlier observed by the NA49 Collaboration. The
cascade evaporation model, FRITIOF model, and UrQMD 1.3 model are used to analyze the data. The dependence of the fluctuations
on nuclear collision centrality is theoretically described without any exotic assumptions. According to the FRITIOF model,
the dependence of the multiplicity fluctuations on the collision centrality is to a large extent governed by fluctuations
in the number of “wounded” nucleons that are associated with the experimental observation conditions. The NA49 Collaboration
data are also described. 相似文献
11.
One of the well-known effects of the asymptotic freedom is splitting of the leading-log BFKL pomeron into a series of isolated
poles in complex angular momentum plane. Following our earlier works we explore the phenomenological consequences of the emerging
BFKL-Regge factorized expansion for the small-x charm (F
2
c
) and beauty (F
2
b
) structure functions of the proton. As we found earlier, the colordipole approach to the BFKL dynamics predicts uniquely
decoupling of subleading hard BFKL exchanges from F
2
c
at moderately large Q
2. We predicted precocious BFKL asymptotics of F
2
c
(x,Q
2) with intercept of the rightmost BFKL pole α
P(0) − 1 = ΔP ≈ 0.4. High-energy open beauty photo- and electroproduction probes the vacuum exchange at much smaller distances and detects
significant corrections to the BFKL asymptotics coming from the subleading vacuum poles. In view of the accumulation of the
experimental data on small −x
F
2
c
and F
2
b
we extended our early predictions to the kinematical domain covered by new HERA measurements. Our structure functions obtained
in 1999 agree well with the determination of both F
2
c
and F
2
b
by the H1 published in 2006 but contradict very recent (2008, preliminary)H1 results on F
2
b
. We present also comparison of our early predictions for the longitudinal structure function F
L
with recent H1 data (2008) taken at very low Bjorken x. We comment on the electromagnetic corrections to the Okun-Pomeranchuk theorem. 相似文献
12.
Alakabha Datta David London Joaquim Matias Makiko Nagashima Alejandro Szynkman 《The European Physical Journal C - Particles and Fields》2009,60(2):279-284
Certain B
s
0→V
1
V
2 decays (V
i
is a vector meson) can be related by flavor SU(3) symmetry to corresponding B
d
0→V
3
V
4 decays. In this paper, we show that the final-state polarization can be predicted in the B
s
0 decay, assuming polarization measurements of the B
d
0 decay. This can be done within the scenario of penguin annihilation (PA), which has been suggested as an explanation of the
unexpectedly large transverse polarization in B→φ
K
*. PA is used to estimate the breaking of flavor SU(3) symmetry in pairs of decays. Two of these for which PA makes a reasonably
precise prediction of the size of SU(3) breaking are (B
s
0→φ
φ,B
d
0→φ
K
0*) and (
). The polarization measurement in the B
d
0 decay can be used to predict the transverse polarization in the B
s
0 decay and will allow for testing of PA as well as the other assumptions in the analysis. 相似文献
13.
M. V. Tokarev 《Physics of Atomic Nuclei》2009,72(3):541-551
New experimental data on inclusive cross section of neutral-vector-meson (ω
0, ϕ, K
S
0) production in proton-proton collisions at = 200 GeV obtained at RHIC are analyzed in the framework of z scaling. Properties of z-presentation are used to predict hadron yields over a wide range of transverse momentum p
T
and collisions energy . The next-to-leading-order perturbative QCD calculations of inclusive cross sections of π
0 mesons produced in pp and collisions over a wide range of and p
T
are compared with ISR, S
pS, RHIC data and predictions of z scaling. The dependence of the spectra in p
T
and z presentations for different parton distribution and fragmentation functions is studied. The sensitivity of the obtained results
to the choice of the renormalization (μ
R
), initial-state factorization (μ
F
), and final-state factorization (fragmentation) (μ
H
) scales is verified. It is shown that self-similar features of particle production dictated by the z scaling give strong restriction on the asymptotic behavior of the inclusive spectra in high-p
T
region.
The text was submitted by the author in English. 相似文献
14.
A. C. dos Reis 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):474-478
The issue of Kπ and ππ
S-wave amplitude is addressed using decays of D-mesons. Model-independent measurements of the phases of the π
+
π
+ and K
-
π
+
S-wave amplitude from D
+→π
-
π
+
π
+ and D
+→K
-
π
+
π
+ decays are discussed. The result indicates a deviation from the phase of the K
-
π
+
S-wave amplitude obtained by scattering experiments. This could be interpreted as an indication of the presence of 3-body final-state
interaction, or in other words, that the phases from production and scattering process cannot be directly compared. 相似文献
15.
Yong-Yeon Keum 《Pramana》2004,63(6):1151-1170
We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two-bodyB-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approach. PQCD
results are compatible with present experimental data for charmless B-meson decays. We predict the possibility of large direct
CP asymmetry in B0 → π+π− (23 +7%) and B0 →K
+π− (− 17 ± 5%). We also investigate the branching ratios, CP asymmetry and isospin symmetry breaking in radiativeB →(K*/ρ)γ decays. 相似文献
16.
We solve the Leggett equations for the BCS-BEC crossover in a three dimensional resonance p-wave superfluid with the symmetry of the A1 phase. We calculate the sound velocity, the normal density, and the specific heat for the BCS domain (μ > 0), for the BEC
domain (μ < 0), and close to the important point μ = 0 in the 100% polarized case. We find the indications of a quantum phase
transition close to the point μ(T = 0) = 0. Deep in the BCS and BEC domains, the crossover ideas of Leggett, Nozieres, and Schmitt-Rink work quite well. We
discuss the spectrum of orbital waves, the paradox of intrinsic angular momentum and the complicated problem of chiral anomaly
in the BCS A1 phase at T = 0. We present two different approaches to the chiral anomaly, based on supersymmetric hydrodynamics and on the formal analogy
with the Dirac equation in quantum electrodynamics. We evaluate the damping of nodal fermions due to different decay processes
in the superclean case at T = 0 and find that a ballistic regime ωτ ≫ 1 occurs. We propose to use aerogel or nonmagnetic impurities to reach the hydrodynamic
regime ωτ ≪ 1 at T = 0. We discuss the concept of the spectral flow and exact cancelations between time derivatives of anomalous and quasiparticle
currents in the equation for the total linear momentum conservation. We propose to derive and solve the kinetic equation for
the nodal quasiparticles in both the hydrodynamic and ballistic regimes to demonstrate this cancelation explicitly. We briefly
discuss the role of the other residual interactions different from damping and invite experimentalists to measure the spectrum
and damping of orbital waves in the A phase of 3He at low temperatures. 相似文献
17.
The dielectron widths of Y(nS)(n = 1, …, 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction.
For Y(nS) (n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580)
and Y(11020) a good agreement with experiment is reached only if the 4S-3D mixing (with a mixing angle θ = 27°± 4°) and 6S-5D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, $
\tilde \Upsilon
$
\tilde \Upsilon
(n
3
D
1) with n = 3, 4, 5 is discussed. In particular, $
\tilde \Upsilon
$
\tilde \Upsilon
(≈11120), originating from the pure 53
D
1 state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e
+
e
− experiments. On the contrary, the widths of pure D-wave states are very small, Γ
ee
(n
3
D
1)≤ 2 eV. 相似文献
18.
V. E. Tarasov V. V. Khabarov A. E. Kudryavtsev V. M. Weinberg 《Physics of Atomic Nuclei》2008,71(8):1410-1423
The Kd reactions are considered in the impulse approximationwithNN final-state interactions (FSI) taken into account. Realistic parameters for the KN phase shifts are used. The “quasi-elastic” energy region, in which the elementary KN interaction is predominantly elastic, is considered. The theoretical predictions are compared with the data on the K
+
d → K
+
pn, K
+
d → K0
pp, K
+
d → K
+
d, and K
+
d total cross sections. The NN FSI effect in the reaction K
+
d → K
+
pn has been found to be large. The predictions for the Kd cross sections are also given for slow kaons, produced from ϕ(1020) decays, as the functions of the isoscalar KN scattering length a
0. These predictions can be used to extract the value of a
0 from the data.
The text was submitted by the authors in English. 相似文献
19.
N. N. Achasov 《Physics of Atomic Nuclei》2007,70(5):862-863
It is argued that the realization of gauge invariance condition as a consequent of cancellation between the ϕ → γf
0 → γπ
0
π
0 resonance contribution and the ϕ → γπ
0
π
0 background one, suggested by A.V. Anisovich et al., Yad. Fiz. 68, 1614 (2005), is misleading.
The text was submitted by the author in English. 相似文献
20.
Corrections of order α
5 and α
6 to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear
structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73
meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P
1/2), and −24 290.69 μeV (2P
3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ12 = 8ΔE
hfs(2S) − ΔE
hfs(1S) = 1.59 meV can be used to test QED predictions. 相似文献