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1.
High-statistics data on the γγ → π0η reaction will make it possible to conclude whether the K
+
K
−-loop rescattering mechanism, γγ → K
+
K
− → a
0(980) → π0η, is the main mechanism of the production of a
0(980) isovector resonance. This mechanism provides a reasonable value of 20–30 nb at the maximum for the manifestation of
a
0(980) in the γγ → π0η cross section. It also gives rise to a noticeable narrowing of the a
0(980) peak to its effective (observed) width ≈20–30 MeV in the γγ → π0η channel. The decay width averaged over the resonance mass distribution is 〈Γα
0 → K
+
K
− → γγ〉πη ≈ 0.13 keV. The experimental confirmation of this scenario would be important evidence in favor of the q
2
$
\bar q
$
\bar q
2 nature of light scalar mesons. 相似文献
2.
The branching ratio for B
s
→ ℓ+ℓ−
γ mode is of the same order as B
s
→ ℓ+ℓ−, since there is no helicity suppression in the 3-body decay mode. New Physics beyond Standard Model may affect these rates
favourably for experimental observation at LHC and simultaneous measurements of the modes B
s
→ μ+μ− and B
s
→ μ+μ−
γ at LHC experiment will indicate the basic nature of the interaction at play. A simulation study has been performed to evaluate
the potential of CMS detector to observe the more difficult mode of B
s
→ μ+μ−γ. An upper limit of 2.08 × 10−7 on the branching ratio is expected to be achieved corresponding to an integrated luminosity of 10 fb−1. 相似文献
3.
In an attempt to explain the recent measurements on the radiative decays of the vector-mesons (V→Pγ), we study the consequences of introducing a small admixture of SU (3) singlet piece in the electromagnetic current. We find
that this leads to an excellent fit of the theory with the new measurements on theV→Pγ decays. However, this addition adversely affects the fit of the leptonic decays of the vector mesons (V→e
+
e
−) and of the radiative decay of the pion (π→2γ). We conclude that the overall fit to the available data does not favour a large (>10%) admixture of the SU(3) singlet. The
decay rates have been calculated in the vectormeson dominance model. At the hadronic vertex (VVP), we assume asymptotic nonet symmetry. The electromagnetic couplings (V−γ) are the ones appropriate to vector-mixing. 相似文献
4.
For aL
∞
(ℝ+)∩L
1
(ℝ+) the truncated Bessel operator B
τ
(a) is the integral operator acting on L
2
[0,τ] with the kernel
where J
ν
stands for the Bessel function with ν>−1. In this paper we determine the asymptotics of the determinant det(I+B
τ
(a)) as τ→∞ for sufficiently smooth functions a for which a(x)≠1 for all x[0,∞). The asymptotic formula is of the form det(I+B
τ
(a))∼G
τ
E with certain constants G and E, and thus similar to the well-known Szeg?-Akhiezer-Kac formula for truncated Wiener-Hopf determinants.
Received: 23 April 2002 / Accepted: 25 September 2002 Published online: 24 January 2003
RID="*"
ID="*" Supported in part by NSF Grant DMS-9970879.
Communicated by J.L. Lebowitz 相似文献
5.
《JETP Letters》2007,85(8):347-352
A precise τ lepton mass measurement performed at the VEPP-4M collider with the KEDR detector is reported. The mass value is
evaluated from the τ+τ− cross section behavior around the production threshold. The result based on 6.7 pb−1 of data is m
τ = 1776.81
−0.23
+0.25
± 0.15 MeV. Using 0.8 pb−1 of data collected at the ψ′ peak, we have also determined that Γ
ee
B
ττ(ψ′) = 9.0 ± 2.6 eV.
The text was submitted by the authors in English. 相似文献
6.
7.
In this paper we examine the possibility of having an exception to the recent observation by L. Randall amd M. Wise, which
states that “a significant branching ratios to both e
+
e
− and γ
γ is possible only if new physics beyond that in the SM couples directly to electrons”. We consider resonances decaying into
diphotons and dielectrons final states predicted in U(1)
B−L
extensions of the SM. We find that these new resonances can’t decay into e
+
e
− and γ
γ final states with comparably measurable branching ratios although such resonances are directly coupled to electrons. 相似文献
8.
M. Aglietta B. Alessandro P. Antonioli F. Arneodo L. Bergamasco A. Campos Fauth C. Castagnoli A. Castellina C. Cattadori A. Chiavassa et al. 《Il Nuovo Cimento C》1992,15(4):441-446
Summary A search for cosmic gamma-ray bursts in the GeV energy range has been performed by means of the EAS-TOP Extensive Air Shower
array at Campo Imperatore (Gran Sasso Laboratories) during the period March–December 1990. In 2566.5 hours of measurement
the obtained upper limit to the rate of bursts of amplitude >2% of the cosmic-ray intensity and time duration τ=1 s, isR≤7.9y−1 (90% c.l.). Assuming for γ-rays a differential energy spectrumS(E
0
)≈E
0
−2.5
, the corresponding upper limit to the energy flux of γ-rays with energy >5 GeV in bursts of duration τ≤1 s is Φ<8.3·10−5erg cm−2. 相似文献
9.
CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed
out that such an absorptive part can be provided ine
+
e
− annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process
, wherel
i
are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine
+
e
− →τ
+
e
− (τ
−
e
+) is shown to be possible at LEP/SLC energies. 相似文献
10.
11.
S. Rai Choudhury A. S. Cornell Naveen Gaur 《The European Physical Journal C - Particles and Fields》2008,58(2):251-259
Flavor changing neutral current (FCNC) decays of the B-meson are a very useful tool for studying possible physics scenarios beyond the standard model (SM), where of the many FCNC
modes radiative, purely leptonic and semi-leptonic decays of the B-meson are relatively clean tests. Within this context, the BELLE collaboration has measured the process B→K
*
γ and also searched for the B→K
1(1270)γ process. Theoretical analyses of these processes are yielding similar values of the relevant form factors. In this work we
have used this upper bound in studying the angular correlations for the related semi-leptonic decay mode B
−→K
1−(1270)(→ρ
0
K
−)ℓ
+
ℓ
−, where we have used the form factors that have already been estimated for the B→K
1(1270)γ mode. Note that the additional form factors that are required were calculated using large energy effective theory (LEET). 相似文献
12.
B. Cameron Reed 《Central European Journal of Physics》2005,3(1):1-7
The ground-state energy of neutral helium is estimated variationally with a trial wavefunction of the form ϕ≈e
−γ(rA/a
o)ne−γ(rB/a
o)n. This model represents a modification of traditional textbook examinations of this problem via inclusion of the power “n”
as a second nonlinear variational parameter in addition to the usual effective nuclear charge γ and leads to an upper-limit
on the ground state energy of −2.86107 E
h
(E
h
=1 hartree) in comparison with the traditional (n=1) result of −2.84766 E
h
. This result represents a reduction of the percentage overestimate from the true ground-state energy (−2.90373 E
h
) of from 1.93 to 1.47. In comparison with the maximum accuracy obtainable from an uncorrelated trial wavefunction, −2.86168
E
h
, the present trial wavefunction reduces the percentage overestimate from 0.49 (n=1) to 0.021. The optimum values of (n, γ)
are determined to be ≈(0.897, 1.825). 相似文献
13.
S. G. Karshenboim V. G. Ivanov U. D. Jentschura G. Soff 《Journal of Experimental and Theoretical Physics》1998,86(2):226-236
We examine the properties of an atomic system consisting of a muon and antimuon. Expressions are derived for the probability
of decay and the hyperfine splitting of the lower levels with allowance for the leading radiative corrections, which are of
relative order α. The results for the lifetimes and the ground-state energy are τ(13
S
1)=1.7907(8)×10−12 s, τ(11
S
0)=0.59547(33)×10−12 s, and E
hfs (1s)=4.23284(35)×107 MHz. The relative probabilities for the various decay channels are calculated; in particular, for the 1 3
S
1 level it is found that Γ (μμ→eeγ)/Γ(μμ→ee)≈15%. Finally, possible applications are discussed.
Zh. éksp. Teor. Fiz. 113, 409–431 (February 1998) 相似文献
14.
V. M. Aul’chenko M. N. Achasov A. V. Bozhenok A. D. Bukin D. A. Bukin S. V. Burdin I. A. Gaponenko V. B. Golubev T. V. Dimova S. I. Dolinskii V. P. Druzhinin M. S. Dubrovin V. N. Ivanchenko P. M. Ivanov A. A. Korol’ S. V. Koshuba A. A. Mamutkin E. V. Pakhtusova S. I. Serednyakov V. A. Sidorov Z. K. Silagadze Yu. V. Usov V. V. Sharyi Yu. M. Shatunov 《JETP Letters》1999,69(2):97-102
A search for the process e
+
e
−→φ(1020)→η″(958) γ in the decay channel η″→π
+
π
−
η, η→γγ was made in an experiment at the VEPP-2M e
+
e
− collider with the SND detector. Analysis confirms the occurrence of φ→η″γ decay with probability B(φ→η″ γ)=(6.7
−2.9
+3.4
)×10−5.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 87–91 (25 January 1999) 相似文献
15.
V. A. Kartoshkin 《Optics and Spectroscopy》2011,110(5):665-671
The interaction of alkali K and Rb atoms that reside in the ground state is considered in the range of collision energies
E = 10−4 to 10−2 au. The singlet (X
1Σ+) and triplet (a
3Σ+) interaction potentials available in the literature are analyzed and modified. For the KRb dimer in the range of interatomic
distances 15–21a
0, we chose analytical representations of the singlet and triplet potentials that more accurately describe the interaction
of alkali Rb and K atoms in the ground state. Complex cross sections of the spin exchange are calculated for the first time
that permit one to calculate the processes of polarization transfer and relaxation times, as well as shifts in the magnetic
resonance frequencies caused by K-Rb spin exchange collisions. 相似文献
16.
Simulation study of χc→J/Ψ+γ detection with J/Ψ→e+e? in pp collisions in the ALICE experiment at LHC
P. González P. Ladrón de Guevara E. López Torres A. Marín E. Serradilla 《The European Physical Journal C - Particles and Fields》2009,61(4):915-903
We present Monte Carlo preliminary results about the feasibility to detect the χ
c
family in p-p collisions at 14 TeV in the ALICE Central Barrel at CERN LHC. The χ
c1 and χ
c2 were forced to decay in the radiative channel J/Ψ+γ→e
+
e
−+γ and were merged with a proton-proton non-biased collision. After Monte Carlo transport and simulation of the detector response,
the e
+, e
− and converted γ were reconstructed and identified in the ALICE ITS, TPC and TRD detectors. Separate signals corresponding to γ from χ
c1 and from χ
c2 were observed. The position and relative weight of the fit to gaussians agreed with the input values within the statistical
limits.
An erratum to this article can be found at 相似文献
17.
Experimentally established mesonic decays ofτ
− lepton have been reexamined with the inclusion of the effects of finite neutrino mass and the associated mass mixing in the
form of Kobayashi-Maskawa mixing matrix. A comparison with the experimentally predicted decay probabilities provides limits
for thev
τ mass which are finite in all decays except for the lower limit in mass mixing case of the decayτ
−→K*− (892)+v
τ for which
MeV. The large error in this value is because of (i) large errors in the experimental values of life time and branching ratio
for this decay and (ii) thekm mixing used in the calculations. The ratio of parity-violating to parity-conserving terms in the differential decay probabilities
of various decays differs slightly from their values corresponding to those with varishingv
τ mass. 相似文献
18.
The synthesis and functionalization of carbon nanoparticles with PEG200 and mercaptosuccinic acid, rendering fluorescent carbon dots, is described. Fluorescent carbon dots (maximum excitation and
emission at 320 and 430 nm, respectively) with average dimension 267 nm were obtained. The lifetime decay of the functionalized
carbon dots is complex and a three component decay time model originated a good fit with the following lifetimes: τ
1 = 2.71 ns; τ
2 = 7.36 ns; τ
3 = 0.38 ns. The fluorescence intensity of the carbon dots is affected by the solvent, pH (apparent pK
a of 7.4 ± 0.2) and iodide (Stern-Volmer constant of 78 ± 2 M−1). 相似文献
19.
E. P. Shabalin 《Physics of Atomic Nuclei》2010,73(11):1908-1915
The unitarization of the amplitude for the decay process K
10 → π+π− and allowance for the rescattering of final-state pions in the decay process K
+ → π+π+π− make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K
+ → π+π+π− decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for
higher order terms of the momentum expansion of the amplitude for the decay process K
+ → π+π+π− leads to the slope-parameter value of g
++−th = 0.2182, which agrees with its experimental counterpart, g
++−exp = 0.2154 ± 0.0035. 相似文献
20.
V. I. Telnov 《Pramana》2007,69(6):957-961
At linear colliders, the e
+
e
− luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs).
In γγ collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In the present damping
ring designs, nominal DR parameters correspond to those required for e
+
e
− collisions. In this note, I would like to stress once again that as soon as we plan the photon collider mode of ILC operation,
the damping ring emittances are dictated by the photon collider requirements — namely, they should be as small as possible.
This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential
improvement of the γγ luminosity. No expert analysis exists as of now, but it seems realistic to obtain a factor five increase of the γγ luminosity compared to the ‘nominal’ DR design.
相似文献