共查询到20条相似文献,搜索用时 46 毫秒
1.
V. V. Andreev 《Physics of Particles and Nuclei Letters》2011,8(4):347-355
The behavior of the running coupling constant α
s
(Q
2) phenomenologically parameterized in the region of Q < 1 GeV is considered within the framework of the Poincare-covariant quark model in a variety of regimes. An analysis was
carried out for pseudoscalar and vector mesons with the lepton masses and decay constants (obtained by the model calculations)
required to match their experimental counterparts. It shows that the constant α
s
is likely to behave with αcrit = α
s
(Q
2 = 0) ∼ 0.667 − 0.821 in the case of a frozen regime and αcrit =0.300 − 0.692 for peaked curves, which follows from the experimental values of the leptonic decay constants and masses. 相似文献
2.
The phenomenology of the low scale U(1)B–L extension of the standard model and its implications at LHC energies is presented. In this model, an extra gauge boson corresponding
to B–L gauge symmetry and an extra SM singlet scalar (heavy Higgs boson) are predicted. We show a detailed analysis of both
heavy and light Higgs bosons decay and production in addition to the possible decay channels of the new gauge boson. We find
that the cross sections of the SM-like Higgs production are reduced by ∼20–30%, while its decay branching ratios remain intact.
The extra Higgs boson has relatively small cross sections and the branching ratios of Z′→l+l- are of order ∼20% to be compared to ∼3% of the SM results. Hence, the search for Z′ is accessible via a clean dilepton signal at LHC. 相似文献
3.
Bianchi Type-I cosmological models containing perfect fluid with time varying G and Λ have been presented. The solutions obtained represent an expansion scalar θ bearing a constant ratio to the anisotropy in the direction of space-like unit vector λ
i
. Of the two models obtained, one has negative vacuum energy density, which decays numerically. In this model, we obtain Λ
∼ H
2, Λ ∼ R
44/R and Λ ∼ T
−2 (T is the cosmic time) which is in accordance with the main dynamical laws for the decay of Λ. The second model reduces to a
static solution with repulsive gravity.
相似文献
4.
S. N. Nakamura D. Tomono Y. Matsuda G. Mason M. Iwasaki K. Ishida T. Matsuzaki I. Watanabe S. Sakamoto K. Nagamine 《Hyperfine Interactions》2001,138(1-4):445-450
The lifetime of the positive muon (τμ
+) can be directly associated with the Fermi Coupling Constant (G
F
), which is one of the most basic parameters of the Standard Model. However, the current experimental accuracy of the τμ
+ is ∼30 ppm and it has not been improved for more than 15 years. We propose a new experiment for a pulsed muon facility such
as RIKEN-RAL to measure the muon lifetime with multi-decay per one time window method. The advantage of our setup, no time
window limitation, enables us to test the exponential decay law (EDL) in the long decay time region at the same time. The
preliminary analysis set a new upperlimit for the EDL deviation in the muon decay. We accumulated ∼1010 muon decays and analysis is in progress.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
T. G. Adiks A. F. Bunkin V. A. Luk’yanchenko S. M. Pershin 《Physics of Wave Phenomena》2008,16(1):1-6
The contribution of impurity fluorescence was determined in the water Raman spectra excited by the second harmonic (λ = 532 nm) of a pulsed Nd:YAG laser. Water samples prepared by different techniques (tap water (undistilled), distilled water,
Milli-Q water, water for injections, and water subjected to cavitation treatment) were investigated. The Raman (bands at ν
2 ∼ 1550 cm−1 and ν
3 ∼ 3400 cm−1) and fluorescence (Stokes shift 2500 cm−1) signals were separated spectrally and according to the differences in the emission kinetics. It was established that all
investigated samples, including distilled and specially purified water for injections, exhibit afterglow. The highest sensitivity
to the presence of impurities was revealed near ∼ 2500 cm−1. The least contribution to the fluorescence signal was found in the water for injections. 相似文献
6.
GRB 070610, which is also named Swift J195509.6+261406, is a peculiar Galactic transient with significant variability on short timescales in both X-ray and optical light curves. One possible explanation is that GRB 070610/Swift J195509.6 + 261406 is a soft gamma-ray repeater (SGR) in our Galaxy. Here, we use the fireball model, which is usually recognized as the standard model of gamma-ray burst (GRB) afterglows, and the energy injection hypothesis to interpret the X-ray and optical afterglow light curves of GRB 070610/Swift J195509.6 + 261406. It is found that the model is generally consistent with observations.
相似文献7.
The time-differential perturbed angular correlation technique was used to investigate quadrupole interactions following the
decay of99Mo as a probe in the intercalation compound graphite-molybdenum pentachloride. Analysis of the 740-(44) 141 keV γ-γ correlation
in99Tc reveals the presence of two sites with static electric field gradient interactions, one of which corresponds to a moderately
damped (δ∼16%), high-frequency interaction (v
q∼630 MHz), the other to a heavily damped (δ∼28%), low-frequency (v
q∼283 MHz) component. 相似文献
8.
K. V. Ivanin A. V. Leont’ev V. S. Lobkov G. M. Safiullin V. V. Samartsev 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(3):290-294
The results from experiments employing coherent femtosecond spectroscopy in a layer of two-dimensional electron gas at the
boundary of the GaAs/AlGaAs heterojunction at room temperature are presented. The decay curves of primary femtosecond photon
echo are obtained. The decoherence time in two-dimensional electron gas depends strongly on the power of the exciting pulse
and varies from 36 to 54 fs. The dephasing time is studied for the first time as a function of the power of exciting pulses
at room temperature. It is established that this dependence obeys the law T
2 ∼ N
−0.22, which differs from the typical law T
2 ∼ N
−1 for unscreened electron-electron interaction in semiconductor crystals. Analysis shows that electron-phonon interaction plays
an important part along with electron-electron interaction. The induced spin gratings in the GaAs/AlGaAs heterostructure are
studied with an eye to their possible application in spintronics. 相似文献
9.
S. S. Novosad I. M. Matviishin I. S. Novosad O. S. Novosad 《Journal of Applied Spectroscopy》2008,75(6):826-831
We have studied the effect of lead dopant on the optical absorption, photoluminescence, and x-ray luminescence spectra, and
the scintillation characteristics of CdI2 at room temperature. The crystals for the study were grown by the Stockbarger-Bridgman method. Activation of CdI2 from the melt by the compound PbI2 leads to the appearance in the absorption spectra in the near-edge region of an activator band at 395–405 nm, which is interpreted
as an A band connected with electronic transitions from the 1S0 state to the 3P1 levels in the Pb2+ ion. For x-ray excitation, CdI2:Pb2+ crystals with optimal dopant concentration (∼1.0 mol%) are characterized by a light yield with maximum in the 570–580 nm
region that is an order of magnitude higher than for CdI2 crystals in the 490–500 nm band. For α excitation, the radioluminescence kinetics for cadmium iodide is characterized by
a very short (∼0.3 nsec) rise time and fast decay of luminescence, with τ1 ≈ 4 nsec and τ2 = 10–76 nsec. Depending on the conditions under which the crystals were obtained, the fast component fraction is 95%–99%.
The crystal is characterized by a similar scintillation pulse in the case of excitation by x-ray pulses. The radioluminescence
pulse shape for CdI2:Pb in the decay stage is predominantly exponential, with luminescence decay time constants τ1 ≈ 10 nsec and τ2 = 200–250 nsec. This system is characterized by low afterglow, at the level for the Bi4G3O12 scintillator. We have demonstrated the feasibility of using CdI2:Pb as a scintillator for detecting α particles.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 825–830, November–December, 2008. 相似文献
10.
Debasish Majumdar 《Pramana》2008,70(1):51-60
The possibility to verify the pseudo-Dirac nature of neutrinos is investigated here via the detection of ultra-high energy
neutrinos from distant cosmological objects like γ-ray bursts (GRBs). The very long baseline and the energy range from ∼TeV to ∼EeV for such neutrinos invoke the likelihood
to probe very small pseudo-Dirac splittings. The expected secondary muons from such neutrinos that can be detected by a kilometer
scale detector such as ICECUBE is calculated and compared with the same in the case of mass-flavour oscillations and for no
oscillation cases. The calculated muon yields indicate that to probe such small pseudo-Dirac splittings one needs to look
for a nearby GRB (red shift z ∼ 0.03 or less) whereas for a distant GRB (z ∼ 1) the flux will be much depleted and such phenomenon cannot be distinguished. Also calculated are the muon-to-shower ratios.
相似文献
11.
Yu. A. Shitov 《Physics of Atomic Nuclei》2006,69(12):2090-2095
The NEMO-3 detector has been taking data in the Fréjus underground laboratory (LSM, France) since February 2003 and is devoted
to the search for neutrinoless double-beta decay (0νββ). After 389 effective days of data collection from February 2003 until September 2004 (Phase I), no evidence for neutrinoless
double-beta decay was found from ∼7 kg of 100Mo and ∼1 kg of 82Se. The corresponding limits for the half-lives are T
1/2(0νββ) > 4.6 × 1023 yr for 100Mo and T
1/2(0νββ) > 1.0 × 1023 yr for 82Se (90% C.L.). They lead to the following limits for the effective Majorana neutrino mass: 〈m
ν〉 < 0.7–2.8 eV for 100Mo and 〈m
ν〉 < 1.8–4.9 eV for 82Se. The half-lives of the two-neutrino double-beta decay (2νββ) have been measured for 100Mo, 82Se, 116Cd, 150Nd, and 96Zr and reported here as well.
on behalf of NEMO Collaboration
The text was submitted by the author in English. 相似文献
12.
Pramod Bhatt E. Carlegrim A. Kanciurzewska M. P. de Jong M. Fahlman 《Applied Physics A: Materials Science & Processing》2009,95(1):131-138
Thin film iron-tetracyanoethylene Fe(TCNE)
x
, x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed
physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron
spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE)
x
is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results.
The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge
transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE)
x
system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T
C
) seen for Fe(TCNE)
x
-type magnets. 相似文献
13.
I. R. Mardaleishvili P. P. Levin V. B. Ivanov 《Russian Journal of Physical Chemistry B, Focus on Physics》2009,3(4):560-566
The kinetics of luminescence and transformation of short-lived products of the photolysis of europium and lanthanum complexes
with thenoyltrifluoroacetone and 1,10-phenanthroline and their mixtures in polymethyl methacrylate films was studied by the
nanosecond laser photolysis method with recording both light emission and absorption. Fast (535 and 585 nm, 5
D
1 → 7
F
0, 7
F
3, decay time 0.7 μs) and slow (613 nm, 5
D
0 → 7
F
2, luminescence rise and decay times 0.7 μs and 0.5 ms, respectively) luminescence was studied. Induced absorption with a maximum
at 600 nm and decay time ∼3 ms was observed; this absorption was assigned to triplet states of the deprotonated form of thenoyltrifluoroacetone.
The dependences of luminescence intensity on the concentration of the components in a mixture of complexes were analyzed,
and synergistic effects of luminescence strengthening were estimated. The kinetics of a decrease in luminescence intensity
during photolysis was studied. Possible mechanisms of a decrease in the relative initial process rate and an increase in the
quasi-stationary value of relative luminescence intensity as the concentration of complexes in the polymer increased were
discussed. 相似文献
14.
15.
K.C. Chung C.S. Wang A.J. Santiago J.W. Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,12(2):161-167
The parameters of the σ-ω-ρ model in the relativistic mean-field theory with nonlinear σ-meson self-interaction are determined
by nuclear-matter properties, which are taken as those extracted by fits to data based on nonrelativistic nuclear models.
The values of the relevant parameters are C
σ
2∼ 94, C
ω
2∼ 32, C
ρ
2∼ 26, b∼ - 0.09, c∼ 1, and the σ-meson mass m
σ∼ 370 MeV, while the value of the calculated nuclear- surface thickness is t∼ 1.4 fm. The field system is shown to be stable, since the σ-meson self-interaction energy is a lower bound in this whole
parameter region with positive c. On the other hand, the effective nucleon mass M* is larger than 0.73M, if the symmetry incompressibility Ks is assumed to be negative and the nuclear-matter incompressibility K0 is kept less than 300 MeV.
Received: 27 June 2001 / Accepted: 5 October 2001 相似文献
16.
A novel ZrO2:Sm3+,Sn4+ phosphor is synthesized by solid state reaction. The ZrO2:Sm3+ does not show afterglow. But, after doping Sn4+, intense red afterglow luminescence is firstly observed in ZrO2:Sm3+,Sn4+ and it can last more than 1000 s at maximum. The afterglow decay curves of ZrO2:Sm3+,Sn4+ are fitted by three exponential components and the decay process consists of initial fast, intermediate and slow decay. The thermoluminescence indicates that the Sn4+ ions induce suitable traps with the depth of 0.436 eV and result in efficient afterglow luminescence of ZrO2:Sm3+,Sn4+. The thermoluminescence filling and fading experiments further confirm the important role of the proper shallow traps induced by doping Sn4+ on the afterglow of ZrO2:Sm3+,Sn4+. 相似文献
17.
Herbert Heinrich Brömer 《Zeitschrift für Physik A Hadrons and Nuclei》1960,158(2):133-141
The intensity decay of negative bands of N 2 + and of first positive bands of N2 in the auroral afterglow has been measured. An explanation, seeming possible for the decay curves of the first ones is proposed. By this the intensity decay in the beginning of the afterglow at high ionic densities is determined by the recombination of N 2 + with electrons. Later, the ambipolar diffusion of the charge carriers to the wall causes the time dependance. A value of the ambipolar diffusion coefficient in nitrogen, derived from the measurements is given by the relationD a ·p ≈ 124cm2 sec?1 Torr. The temperature of the charge carriers is estimated to be 313? K. The intensity decay of the pos. group in the afterglow seems mainly to be due to the diffusion of metastable particles to the wall. 相似文献
18.
Intergalactic magnetic fields are assumed to have been spontaneously generated at the reheating stage of the early Universe,
due to vacuum polarization of non-Abelian gauge fields at high temperature. The fact that the screening mass of this type
of fields has zero value was discovered recently. A procedure to estimate their field strengths, B(T), at different temperatures is here developed, and the value B(T
ew)∼1014 G at the electroweak phase transition temperature is derived by taking into consideration the present value of the intergalactic
magnetic field strength, B
0∼10−15 G, coherent on the ∼1 Mpc scale. As a particular case, the standard model is considered and the field scale at high temperature
is estimated in this case. Model-dependent properties of the phenomena under investigation are briefly discussed, too. 相似文献
19.
We have derived the so-called gap equation, which determines the upper critical magnetic field, perpendicular to conducting chains of a quasi-one-dimensional superconductor. By analyzing this equation at low temperatures, we have found that the calculated angular dependence of the upper critical magnetic field is qualitatively different than that in the so-called effective mass model. In particular, our theory predicts a non-analytical angular dependence of the upper critical magnetic field, H c2(0) − H c2(α) ∼ α3/2, when magnetic field is close to some special crystallographic axis and makes an angle α with it. We discuss possible experiments on the superconductor (DMET)2I3 to discover this non-analytical dependence. 相似文献
20.
L. Theußl R.F. Wagenbrunn B. Desplanques W. Plessas 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):91-101
π and η decay modes of light baryon resonances are investigated within a chiral quark model whose hyperfine interaction is
based on Goldstone-boson exchange. For the decay mechanism a modified version of the 3
P
0 model is employed. Our primary aim is to provide a further test of the recently proposed Goldstone-boson exchange constituent
quark model. We compare the predictions for π and η decay widths with experiment and also with results from a traditional
one-gluon exchange constituent quark model. The differences between nonrelativistic and semirelativistic versions of the constituent
quark models are outlined. We also discuss the sensitivity of the results on the parameterization of the meson wave function
entering the 3
P
0 model.
Received: 11 May 2001 / Accepted: 17 September 2001 相似文献