共查询到20条相似文献,搜索用时 546 毫秒
1.
Kh. M. Beshtoev 《Physics of Particles and Nuclei Letters》2009,6(5):397-402
Usually it is supposed that Majorana neutrino produced in the superposition state χ
L
= ν
L
+ (ν
L
)
c
and then follows the neutrinoless double beta decay. But since the standard weak interactions are chiral invariant then neutrino
at production has definite helicity (ν
L
and (ν
L
)
c
have opposite spirality). Then these neutrinos are separately produced and their superposition state cannot appear. Thus
we see that for unsuitable helicity the neutrinoless double β decay is not possible even if it is supposed that neutrino is
a Majorana particle (i.e. there is not a lepton number which is conserved). Also transition of Majorana neutrino ν
L
into antineutrino (ν
L
)
c
at their oscillations is forbidden since helicity in vacuum holds. Transition Majora neutrino ν
L
into (ν
R
)
c
(i.e., ν
L
→ (ν
R
)
c
) at oscillations is unobserved since it is supposed that mass of (ν
R
)
c
is very big. If neutrino is a Dirac particle there can be transition of ν
L
neutrino into (sterile) antineutrino $
\bar v_R
$
\bar v_R
(i.e., ν
L
→ $
\bar v_R
$
\bar v_R
) at neutrino oscillations if there takes place double violation of lepton number. It is necessary also to remark that introducing
of a Majorana neutrino implies violation of global and local gauge invariance in the standard weak interactions. 相似文献
2.
Yu. A. Gornushkin 《Physics of Particles and Nuclei》2011,42(4):553-557
The OPERA experiment at the underground Gran Sasso Laboratory (LNGS) has to perform the first detection of neutrino oscillations
in appearance mode through the direct observation of νμ → ντ. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy,
long-baseline CERN neutrino beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried
out in 2008–2009 with the first candidate event νμ → gvτ recently detected. 相似文献
3.
Xue-Qian Li Yong Liu Zheng-Tao Wei Liang Tang 《The European Physical Journal C - Particles and Fields》2008,56(1):97-103
In a new measurement on neutrino oscillations, νμ→νe, the MiniBooNE Collaboration observes an excess of electron-like events at low energy and the phenomenon may demand an explanation
that obviously is beyond the oscillation picture. We propose that the heavier neutrino, ν2, decaying into a lighter one, ν1, via the transition process νμ→νe+X, where X denotes any light products, could be a natural mechanism. The theoretical model we employ here is the unparticle
scenario established by Georgi. We have studied two particular modes and νμ→νe+ν̄e+νe. Unfortunately, the number coming out of the computation is too small to explain the observation. Moreover, our results are
consistent with the cosmology constraint on the neutrino life time and the theoretical estimation made by other groups; therefore,
we can conclude that even though neutrino decay seems plausible in this case, it indeed cannot be the source of the peak at
lower energy observed by the MiniBooNE Collaboration and there should be other mechanisms responsible for the phenomenon. 相似文献
4.
Kh. M. Beshtoev 《Physics of Particles and Nuclei Letters》2007,4(6):471-476
In the standard theory of neutrino oscillations, it is supposed that physically observed neutrino states ν
e
, νμ, ντ, have no definite masses, that they are initially produced as a mixture of the ν1, ν2, ν3 neutrino states (i.e., they are produced as a wave packet), and that neutrino oscillations are the real ones. Then, this
wave packet must decompose at a definite distance into constituent parts and neutrino oscillations must disappear. It was
shown that these suppositions lead to violation of the law of energy and momentum conservation. An alternative scheme of neutrino
oscillations obtained within the framework of particle physics has been considered, where the above mentioned shortcomings
are absent, the oscillations of neutrinos with equal masses are the real ones, and the oscillations of neutrinos with different
masses are the virtual ones. Expressions for probabilities of neutrino transitions (oscillations) in the alternative (corrected)
scheme are given.
The text was submitted by the author in English. 相似文献
5.
B. A. Popov 《Physics of Atomic Nuclei》2004,67(11):1942-1947
The results of the search for ν
μ
→ν
e
oscillations in the NOMAD experiment at CERN are presented. The experiment looked for the appearance of ν
e
in a predominantly ν
μ
wideband neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are Δm
2<0.4 eV2 for maximal mixing and sin2(2θ)<1.4×10−3 for large Δm
2. This result excludes the LSND allowed region of oscillation parameters with Δm
2≳10 eV2.
From Yadernaya Fizika, Vol. 67, No. 11, 2004, pp. 1967–1972.
Original English Text Copyright ? 2004 by Popov.
This article was submitted by the author in English.
The author represents the NOMAD Collaboration 相似文献
6.
In the framework of a left–right model containing mirror fermions with gauge group SU(3)
C
⊗SU(2)
L
⊗SU(2)
R
⊗U(1)
Y′, we estimate the neutrino masses, which are found to be consistent with their experimental bounds and hierarchy. We evaluate
the decay rates of the Lepton Flavor Violation (LFV) processes μ→eγ, τ→μγ and τ→eγ. We obtain upper limits for the flavor-changing branching ratios in agreement with their present experimental bounds. We
also estimate the decay rates of heavy Majorana neutrinos in the channels N→W
±
l
∓, N→Zν
l
and N→Hν
l
, which are roughly equal for large values of the heavy neutrino mass. Starting from the most general Majorana neutrino mass
matrix, the smallness of active neutrino masses turns out from the interplay of the hierarchy of the involved scales and the
double application of seesaw mechanism. An appropriate parameterization on the structure of the neutrino mass matrix imposing
a symmetric mixing of electron neutrino with muon and tau neutrinos leads to tri-bimaximal mixing matrix for light neutrinos. 相似文献
7.
Maury Goodman 《Pramana》2004,62(2):229-240
Following incredible recent progress in understanding neutrino oscillations, many new ambitious experiments are being planned
to study neutrino properties. The most important may be to find a non-zero value of θ13. The most promising way to do this appears to be to measurev
μ →v
e oscillations with anE/L near Δm
atmo
2
. Future neutrino experiments are great. 相似文献
8.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》1997,85(1):13-16
We consider axion formation processes in the synchrotron (e
−→e
−
a) and annihilation (e
−
e
+→a) channels in a constant crossed field F
μν
Fμν=Fμν*F
μν
=0, which approximates constant fields of other configurations in the ultrarelativistic asymptotic limit. The probability
and intensity of axion emission are obtained, and we analyze the energy and field asymptotics. A comparison with the characteristic
neutrino channel
yields the constraints on the axion mass and the energy scale for Peccei-Quinn symmetry breaking. Possible astrophysical
applications are discussed.
Zh. éksp. Teor. Fiz. 112, 25–31 (July 1997) 相似文献
9.
C. Jollet 《Physics of Atomic Nuclei》2006,69(11):1872-1875
The aim of the OPERA experiment is to provide unambiguous evidence for the ν
μ ↔ ν
τ oscillation by looking at the appearance of ν
τ in a pure ν
μ beam. This oscillation will be sought in the region of the oscillation parameters indicated by the atmospheric neutrino results.
The experiment is part of the CNGS (CERN Neutrino beam to Gran Sasso) project. The ν
μ beam produced at CERN will be sent towards the Gran Sasso underground laboratory, where the OPERA detector is under construction.
The detector, the physics potential, and performance for neutrino oscillation studies including the subleading ν
μ ↔ ν
ε search are presented.
The text was submitted by the author in English. 相似文献
10.
M. Sioli 《Physics of Atomic Nuclei》2006,69(11):1842-1846
The energy spectrum of neutrino-induced upward-going muons in MACRO has been analyzed in terms of effects of violating relativity
principles, keeping standard mass-induced atmospheric neutrino oscillations as the dominant source of ν
μ → ν
τ transitions. The data disfavor these exotic possibilities even at a subdominant level, and stringent 90% C.L. limits are
placed on the Lorentz invariance violation parameter |Δυ| < 6 × 10−24 at sin(2ϑυ) = 0 and |Δυ| < (2.5–5) × 10−26 at sin(2ϑυ) = ±1. These limits can also be reinterpreted as upper bounds on the parameters describing violation of the equivalence principle.
The text was submitted by the author in English. 相似文献
11.
V. P. Efrosinin 《Physics of Atomic Nuclei》2007,70(11):1926-1930
The possible sources of one-photon radiation as a background for the quasi-elastic reaction ν
μ
+ n → μ− + p are considered. They are relevant in experiments on determination of oscillation parameters at low neutrino energies (E
ν
∼ 1 GeV). The estimation for the cross section of the reaction ν
μ
+ n → μ
− + p + γ is given at E
ν
lab = 0.7 GeV as 0.65% of the corresponding cross section of quasielastic reaction. The mechanisms of quasi-elastic reaction
are also considered at low neutrino energies on a quark level.
The text was submitted by the authors in English. 相似文献
12.
Bipin Singh Koranga P. Gaira Vinod Kumar 《International Journal of Theoretical Physics》2011,50(2):413-417
We study the Planck scale effects in the neutrino sector on the asymmetry between T-conjugate oscillation probabilities. ΔP
T
=P(ν
α
→ν
β
)−P(ν
β
→ν
α
), in a three flavor neutrino mixing. In this paper, we discuss some aspect of T violation effects in three flavor neutrino
oscillation. 相似文献
13.
The quasi-elastic contribution of the nuclear inclusive electron scattering model developed in [A. Gil, J. Nieves, and E.
Oset: Nucl. Phys. A 627 (1997) 543] is extended to the study of electroweak charged current induced nuclear reactions at intermediate energies of
interest for future neutrino oscillation experiments. The model accounts for long-range nuclear (RPA) correlations, final
state interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino
energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions
12C(ν
μ
, μ
−)X and 12C(ν
e, e−)X near threshold are also given.
Presented by M. Valverde at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’05), Corfu, Greece, September
26–29, 2005. 相似文献
14.
In this note, we present preliminary results on the study of the quasielastic reaction ν
μ
n → μ−
p using the full set of NOMAD neutrino data. We perform a measurement of the total cross section of this process, normalizing
to deep-inelastic scattering events selected from the same data sample. The measured cross section is found to be about 20%
smaller than the world average of previous bubble chamber experiments. The analysis is still in progress since it is important
to estimate the systematic uncertainties.
for the NOMAD Collaboration
The text was submitted by the authors in English. 相似文献
15.
If the neutrino has a magnetic moment in the interval 10−13μB < μ
ν
< 10−12 μB and if a magnetic field of strength about 1014 G exists in the supernova envelope, the effect of a pulsation of a neutrino signal from a supernova may arise owing to a
ν
L
→ ν
R
resonance transition in the envelope magnetic field. 相似文献
16.
A.E. Ball A. Braem L. Camilleri A. Catinaccio G. Chelkov F. Dydak A. Elagin P.K. Frandsen M. Gostkin A. Grant A. Guskov C. Joram Z. Krumshteyn H. Müller H. Postema M. Price T. Rovelli D. Schinzel J. Séguinot G. Valenti R. Voss J. Wotschack A. Zhemchugov 《The European Physical Journal C - Particles and Fields》2007,49(4):1117-1142
Today’s greatest challenge in accelerator-based neutrino physics is to measure the mixing angle θ13 which is known to be much smaller than the solar mixing angle θ12 and the atmospheric mixing angle θ23. A non-zero value of the angle θ13 is a prerequisite for observing CP violation in neutrino mixing. In this paper, we discuss a deep-sea neutrino experiment
with 1.5 Mt fiducial target mass in the Gulf of Taranto with the prime objective of measuring θ13. The detector is exposed to the CERN neutrino beam to Gran Sasso in off-axis geometry. Monochromatic muon neutrinos of ≈
800 MeV energy are the dominant beam component. Neutrinos are detected through quasi-elastic, charged-current reactions in
sea water; electrons and muons are detected in a large-surface, ring-imaging Cherenkov detector. The profile of the seabed
in the Gulf of Taranto allows for a moveable experiment at variable distances from CERN, starting at 1100 km. From the oscillatory
pattern of the disappearance of muon neutrinos, the experiment will measure sin2θ23 and especially Δm2
23 with high precision. The appearance of electron neutrinos will be observed with a sensitivity to P(νμ→νe) as small as 0.0035 (90% CL) and sin2θ13 as small as 0.0019 (90% CL; for a CP phase angle δ=0° and for normal neutrino mass hierarchy). 相似文献
17.
Yu. I. Romanov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):818-820
The flavor composition of the solar beryllium neutrino was analyzed using schemes that include the new (heavy) neutrino (ν4) at a negligible angle of mixing with the light partners ν
e
, νμ, and ντ. 相似文献
18.
Using the data of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic
decays D+→K-π+e+νe, D0→K̄0π-e+νe, D+→K̄*0e+νe and D0→K*-e+νe. The absolute branching fractions for the decays are measured to be BF(D+→K-π+e+νe)=(3.50±0.75±0.27)%, BF(D0→K̄0π-e+νe)=(2.61±1.04±0.28)%, BF(D+→K̄*0e+νe)=(5.06±1.21±0.40)% and BF(D0→K*-e+νe)=(2.87±1.48±0.39)%. The ratio of the vector to pseudoscalar semileptonic decay rates Γ(D+→K̄*0e+νe)/Γ(D+→K̄0e+νe) is determined to be 0.57±0.17±0.02. 相似文献
19.
A. N. Ivanov H. Oberhummer N. I. Troitskaya M. Faber 《The European Physical Journal A - Hadrons and Nuclei》2000,8(2):223-250
A dynamics of low-energy nuclear forces is investigated for low-energy electromagnetic and weak nuclear reactions with the
deuteron in the Nambu-Jona-Lasinio model of light nuclei by example of the neutron-proton radiative capture (M1-capture) n
+ p → D + γ, the photomagnetic disintegration of the deuteron γ + D → n + p and weak reactions of astrophysical interest. These are the solar proton burning p + p → D + e+ + ν
e, the pep-process p + e− + p → D + ν
e and the neutrino and antineutrino disintegration of the deuteron caused by charged ν
e + D → e− + p + p, + D → e+ + n + n and neutral ν
e() + D → ν
e() + n + p weak currents. 相似文献
20.
Using a data sample of integrated luminosity of about 33 pb-1 collected around 3.773 GeV with the BESII detector at the BEPC collider, the semileptonic decays D+→φe+νe, D+→φμ+νμ and the hadronic decay D+→φπ+ are studied. The upper limits of the branching fractions are set to be BF(D+→φe+νe)<2.01% and BF(D+→φμ+νμ)<2.04% at the 90% confidence level. The ratio of the branching fractions for D+→φπ+ relative to D+→K-π+π+ is measured to be 0.057±0.011±0.003. In addition, the branching fraction for D+→φπ+ is obtained to be (5.2±1.0±0.4)×10-3. 相似文献