共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
R. Escribano 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):454-457
The scalar contributions to the radiative decay φ→K
0ˉ0
γ are studied within the framework of the Linear Sigma Model (LσM). Theoretical predictions for the associated subprocesses φ→f
0
γ and φ→a
0
γ as well as the ratio φ→f
0
γ/a
0
γ are also given. 相似文献
3.
V.V. Anisovich A.V. Sarantsev 《The European Physical Journal A - Hadrons and Nuclei》2003,16(2):229-258
We present the results of the current analysis of the partial wave IJ
PC = 00+ + based on the available data for meson spectra ( ππ, KˉK,ηη,η,ππππ). In the framework of the K-matrix approach, the analytical amplitude has been reconstructed in the mass region 280 MeV < < 1900 MeV. The following scalar-isoscalar states are seen: comparatively narrow resonances f
0(980), f
0(1300), f
0(1500), f
0(1750) and the broad state f0(1200-1600). The positions of the amplitude poles (masses and total widths of the resonances) are determined as well as pole
residues (partial widths to meson channels ππ, KˉK,ηη,η,ππππ). The fitted amplitude gives us the positions of the K-matrix poles (bare states) and the values of bare-state couplings to meson channels thus allowing the quark-antiquark nonet
classification of bare states. On the basis of the obtained partial widths to the channels ππ, KˉK,ηη,η, we estimate the quark/gluonium content of f
0(980), f
0(1300), f
0(1500), f
0(1750), f0(1200-1600). For f
0(980), f
0(1300), f
0(1500) and f
0(1750), their partial widths testify the qˉq origin of these mesons though being unable to provide precise evaluation of the possible admixture of the gluonium component
in these resonances. The ratios of the decay coupling constants for the f0(1200-1600) support the idea about the gluonium nature of this broad state.
Received: 14 May 2002 / Accepted: 20 August 2002 / Published online: 11 February 2003
RID="a"
ID="a"e-mail: anisovic@thd.pnpi.spb.ru
Communicated by A. Sch?fer 相似文献
4.
E. N. Elekina A. A. Krutov A. P. Martynenko 《Physics of Particles and Nuclei Letters》2011,8(4):331-336
On the basis of quasi-potential approach to the bound state problem in QED we calculate the vacuum polarization, recoil and
structure corrections of orders α5 and α6 to the fine splitting interval ΔE
fs = E(2P
3/2) − E(2P
1/2) in muonic 24He ion. The resulting value ΔE
fs = 146180.68 μeV provides reliable guideline in performing a comparison with the relevant experimental data. 相似文献
5.
We discuss coherent and incoherent φ -meson photoproduction off the deuteron at low energy and small momentum transfer with
the aim to check whether the recent experimental data need for their interpretation an inclusion of exotic channels. Our analysis
of the differential cross-section and spin-density matrix elements shows that new data on the γD → φX reaction at E
γ ∼ 2 GeV may be understood on the basis of conventional dynamics. 相似文献
6.
P. Mohr 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):23-28
α-decay half-lives for 104, 105, 106Te and 108, 109, 110Xe close above the doubly-magic 100Sn are calculated from systematic double-folding potentials. The derived α preformation factors are compared to results for
212, 213, 214Po and 216, 217, 218Rn above the doubly-magic 208Pb. α-decay energies of Q
α = 5.42±0.07MeV and 4.65±0.15MeV are predicted for 104Te and 108Xe; the corresponding half-lives are T
1/2 ≈ 5ns for 104Te and of the order of 60μs for 108Xe. Additionally, the properties of rotational bands in 104Te are analyzed, and the first excited 2+ state in 104Te is predicted at E
x = 650±40keV; it decays preferentially by γ emission with a reduced transition strength of 10 Weisskopf units to the ground
state of 104Te and with a minor branch by α emission to the ground state of 100Sn. 相似文献
7.
On the basis of quasipotential approach to the bound state problem in QED we calculate the vacuum polarization, relativistic,
recoil, structure corrections of orders α
5 and α
6 to the fine structure interval ΔE
fs = E(2P
3/2) − E(2P
1/2) and to the hyperfine structure of the energy levels 2P
1/2 and 2P
3/2 in muonic 23He ion. The resulting values ΔE
fs = 144 803.15 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
1/2) = −58 712.90 μeV, Δ$
\tilde E
$
\tilde E
hfs(2P
3/2) = −24 290.69 μeV provide reliable guidelines in performing a comparison with the relevant experimental data. 相似文献
8.
H. Naik R.J. Singh R.H. Iyer 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):495-507
Charge distribution studies for heavy-mass fission products were carried out in the fast-neutron-induced fission of 232Th, 238U, 240Pu and 244Cm using radiochemical and gamma-ray spectrometric techniques. The width parameter( σZ/σA), the most probable charge/mass ( Z
P/A
P), the charge polarization (ΔZ) and the slope of charge polarization [ δ(ΔZ)/δA
′] as a function of the fragment mass (A
′) were deduced. The average charge dispersion parameter ( 〈σZ〉) and proton odd-even effect ( δp) were also obtained for these fissioning systems. The 〈σZ〉 and δp values in the fissioning systems 241Pu * and 245Cm * were determined for the first time. The δ(ΔZ)/δA
′ value is also determined for the first time in the fissioning systems 239U * , 241Pu * and 245Cm * . These data along with the literature data for even-Z fissioning systems such as 230Th * , 232Th * , 233U * , 234U * , 236U * , 238U * , 239Pu * , 240Pu*, 242Pu * , 246Cm * , 250Cf * and 252Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from the saddle to the scission point. The
role of the excitation energy in low-energy fission is also discussed.
Received: 26 July 2002 / Accepted: 3 December 2002 / Published online: 3 April 2003
RID="a"
ID="a"Present address: Emeritus Scientist (CSIR) Bhabha Atomic Research Centre, Nuclear Recycle Group, WIP Building, Trombay, Mumbai-400085, India;
e-mail: rhiyer@magnum. barc.ernet.in
Communicated by D. Schwalm 相似文献
9.
The narrow D
s0
* (2317) and broad D
0
* (2300-2400) charmed scalar mesons and their radial excitations are described in a coupled-channel quark model that also reproduces
the properties of the light scalar nonet. All two-meson channels containing ground-state pseudoscalars and vectors are included.
The parameters are chosen fixed at published values, except for the overall coupling constant λ, which is fine-tuned to reproduce the D
s0
* (2317) mass, and a damping constant α for subthreshold contributions. Variations of λ and D
0
* (2300-2400) pole postions are studied for different α values. Calculated cross-sections for S-wave DK and Dπ scattering, as well as resonance pole positions, are given for the value of α that fits the light scalars. The thus predicted radially excited state D
s0
*′(2850), with a width of about 50MeV, seems to have been observed already. 相似文献
10.
A. S. Rinat M. F. Taragin M. Viviani 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):415-416
We use the relation between Structure Functions (SFs) of nuclei A and nucleons N in order to fomulate a criterion which isolates the QE part out of the total inclusive cross-section. From data points around
the QEP we extract the reduced neutron magnetic form factor 〈α
n = G
M
n/μ
n
G
d〉. The latter shows an unexpected decrease up to Q
2 = 10GeV^2, the largest measured. 相似文献
11.
The rapid solidification of Al-30%Cu-18%Ag ternary alloy is investigated by using the free fall method. Its solidified microstructure
is composed of θ(Al2Cu), α(Al) and ξ(Ag2Al) phases. The liquidus temperature and solidus temperature are determined as 778 and 827 K, respectively. The alloy melt
undercooled amounts up to ΔT
Max=171 K (0.20T
L). Its microstructural evolution is investigated based on the theoretical analysis of undercooling behavior and nucleation
mechanics. It is found that the undercooling increases with the decrease of the diameter of the alloy droplet. When ΔT<78 K, the primary θ(Al2Cu) phase of the alloy grows into coarse dendrite. When 78 K⩽ΔT⩽171 K, its refined θ(Al2Cu) phase grows alternatively with α(Al) phase. Once ΔT⩾171 K, its microstructure is characterized by the anomalous (θ+α+ξ) ternary eutectic.
Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105) 相似文献
12.
Jiangyong Jia 《The European Physical Journal C - Particles and Fields》2009,62(1):255-264
We review the di-hadron correlation results from RHIC. A consistent physical picture was constructed based on the correlation
landscape in p
T
, Δφ, Δη and particle species. We show that the data are consistent with competition between fragmentation of survived jets and response
of the medium to quenched jets. At intermediate p
T
where the medium response are important, a large fraction of trigger hadrons do not come from jet fragmentation. We argue
that these hadrons can strongly influence the interpretation of the low p
T
correlation data. We demonstrate this point through a simple geometrical jet absorption model simulation. The model shows
that the correlation between medium response hadrons dominates the pair yield and mimics the double hump structure of the
away-side Δφ distribution at low p
T
. This correlation was also shown to lead to complications in interpreting the results on reaction plane dependence and three
particle correlations. Finally, we briefly discuss several related experimental issues which are important for proper interpretations
of the experimental data. 相似文献
13.
D. S. Armstrong 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):451-455
The nucleon's strange electric and magnetic form factors G
E
s and G
M
s can be probed via parity-violating electron scattering. The HAPPEX Collaboration has made new measurements of the parity-violating
asymmetry A
PV in elastic scattering of 3GeV electrons off hydrogen and 4He targets with 〈θlab〉 ≈ 6.0° . For 4He the preliminary result is A
PV = (+ 6.43±0.23(stat)±0.22(syst))×10-6 . For hydrogen the preliminary result is A
PV = (- 1.60±0.12(stat)±0.05(syst))×10-6 . From these values we extract G
s
E = 0.004±0.014±0.013 at 〈Q
2〉 = 0.077 GeV/c^2 , and G
s
E +0.09G
s
M = 0.004±0.011±0.005 at 〈Q
2〉 = 0.109 GeV/c^2 , both consistent with zero, providing stringent new limits on the role of strange quarks in the vector
structure of the nucleon. 相似文献
14.
V. V. Gorbatenko V. I. Kudryash B. N. Prasolov S. A. Gorbatenko 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(10):1313-1316
The contributions to the amplitudes of the harmonic components of the output signal of the Soyer-Tower circuit from charging
the reference capacitor with capacitive current and the conduction current of an investigated specimen are separated via the
harmonic analysis of repolarization in a Rb2ZnCl4 crystal in the ferroelectric phase near the phase transition temperature T
c
. Harmonic analysis of the dielectric hysteresis loops obtained when the specimen was affected by an electric field whose
intensity E
in changed according to harmonic law with amplitude E
m
showed that at E
m
> E
coer (where E
coer is the intensity of the coercive field), the process of repolarization starts and stops when E
in reaches values of E
m
sin(φ0 − α0) and E
m
sin(φ0 + α0), respectively (where φ0 is the shift of phases between the voltage of the harmonic signal source and the voltage of the first harmonic in the reference
capacitor in the Soyer-Tower circuit, and α0 is the phase corresponding to the normalized duration of repolarization). When the current value of intensity E
in coincides with E
c
= E
m
sinφ0, the direction of polarization reverses. The increase in E
c
when T
c
is approached is shown to be the reason for the anomalous temperature-independent behavior of E
coer. 相似文献
15.
L. J. Kaufman 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):501-503
The HAPPEX Collaboration at Jefferson Lab has measured the transverse beam spin asymmetries (AT) for elastic electron scattering from proton and 4He targets. The experiment was conducted using a vertically polarized electron beam of energy ∼ 3 GeV, at a Q
2 ∼ 0.1 GeV^2 and a scattering angle θlab ∼ 6° . The preliminary results are reported here. The 4He measurement is the first measurement of AT from a nucleus. AT for 4He is non-negligible; therefore, it will be necessary to make measurements of AT for future parity-violating experiments using nuclear targets. 相似文献
16.
We present an estimate of the cross-section for the exclusive production of a ρL
0-meson pair in e+e- scattering, which will be studied in the future high-energy International Linear Collider. For this aim, we complete calculations
of the Born order approximation of the amplitudes γ*
L,T(Q1
2)γ*
L,T(Q2
2)→ρL
0ρL
0, for arbitrary polarization of virtual photons and longitudinally polarized mesons, in the kinematical region s≫-t,Q1
2,Q2
2. These processes are completely calculable in the hard region Q1
2,Q2
2≫Λ2
QCD, and we perform most of the calculations in an analytical way. The resulting cross-section turns out to be large enough for
this process to be measurable with foreseen luminosity and energy, for Q1
2 and Q2
2 in the range of a few GeV2. 相似文献
17.
A differential thermal analysis ΔT
y
(T) in vacuum has been performed, and the temperature gradient ΔT
x
(T) along the Ag2Se sample during the transition α → β has been studied. It has been shown that the transitions α → α′ and β′ → β are displacive
transitions and that the transition α′ → β′ is a reconstructive transition. It has been found that the temperature gradient
along the sample during the transition α′ → β′ passes through a deep minimum due to a strong increase in the specific heat
capacity. 相似文献
18.
A. A. Krutov A. P. Martynenko 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(2):163-175
On the basis of the perturbation theory in the fine structure constant α and the ratio of the electron to muon masses we calculate one-loop vacuum polarisation and electron vertex corrections and
the nuclear structure corrections to the hyperfine splitting of the ground state of the muonic helium atom (μ e
3
2He). We obtain total results for the ground state hyperfine splitting Δ
ν
hfs
= 4166.648 MHz which improves the previous calculation of Lakdawala and Mohr due to new corrections of orders α
5 and α
6. The remaining differences between our theoretical result and experimental value of the hyperfine splitting lie in the range
of theoretical and experimental errors and require the subsequent investigation of higher order corrections. 相似文献
19.
S. Pacetti 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):665-671
We define a general procedure, based on analyticity and dispersion relations, to estimate low-energy amplitudes for processes
like: φ→e
+
e
-
M and φ→γM, starting from cross-section data on e
+
e
-→φM, where M is a generic light scalar or pseudoscalar meson. In particular this procedure is constructed to obtain predictions on the
radiative decay rate which are crucially linked on the assumed quark structure for the meson M under consideration. Three cases are analyzed: M = η, M = f
0(qˉ) and M = f
0(qqˉ). While in the η case the estimate of the branching fraction for the radiative decay φ→ηγ is in agreement with the data, in the case of f
0, such agreement is obtained only under the hypothesis of a tetraquark scalar meson. 相似文献
20.
M. V. Gorev E. V. Bogdanov I. N. Flerov A. G. Kocharova N. M. Laptash 《Physics of the Solid State》2010,52(1):167-175
The thermal expansion along the principal crystallographic axes of the (NH4)2WO2F4 and (NH4)2MoO2F4 oxyfluorides has been studied. The anomalous behavior of α
i
(T) due to the phase transitions has been revealed at T
1 = 271.4 K and T
2 ≈ 180 K for the molybdate and at T
1 = 201.5 K and T
2 ≈ 161 K for the tungstate. The quantities dT/dp and dT/dσ
i
, which characterize the dependence of the phase transition temperatures on the hydrostatic and uniaxial pressures, have been
determined from analyzing the results of studies of the thermal expansion and heat capacity with the use of the Pippard relations.
The p-T and α
i
-T phase diagrams reflect different characters of the influence of the pressure on the stability of the initial and distorted
phases of the oxyfluorides. The magnitudes of the extensive and intensive barocaloric effects determined in the vicinity of
the structural phase transitions are as follows: ΔS
BCE varies from approximately −10 to −17 J/mol K and ΔT
AD ≈ 8−17 K for the molybdate and ΔS
BCE varies from approximately −10 to −17 J/mol K and ΔT
AD ≈ 8−13 K for the tungstate. 相似文献