5,195 research outputs found
Scalar Sector in the Minimal Supersymmetric 3-3-1 model
We consider the minimal supersymmetric extension of the 3-3-1 model and we
study the mass spectra in the scalar sector of this model without the
anti-sextet. We show that all our lighest scalars are in agreement with the
experimental limits.Comment: It was included on the introduction of the article the motivation to
> study the model, and we moved the sections 4.1 and 4.2 to the appendix. It
has 22 pages, 9 figures. It was accepted to be published at International
Journal of Modern Physics
Updated Estimate of the Muon Magnetic Moment Using Revised Results from e+e- Annihilation
A new evaluation of the hadronic vacuum polarization contribution to the muon
magnetic moment is presented. We take into account the reanalysis of the
low-energy e+e- annihilation cross section into hadrons by the CMD-2
Collaboration. The agreement between e+e- and tau spectral functions in the pi
pi channel is found to be much improved. Nevertheless, significant
discrepancies remain in the center-of-mass energy range between 0.85 and 1.0
GeV, so that we refrain from averaging the two data sets. The values found for
the lowest-order hadronic vacuum polarization contributions are a_mu[had,LO] =
(696.3 +- 6.2[exp] +- 3.6[rad])e-10 (e+e- -based) and a_mu[had,LO] = (711.0 +-
5.0[exp] +- 0.8[rad] +- 2.8[SU2])e-10 (tau-based), where the errors have been
separated according to their sources: experimental, missing radiative
corrections in e+e- data, and isospin breaking. The corresponding Standard
Model predictions for the muon magnetic anomaly read a_mu = (11,659,180.9 +-
7.2[had] +- 3.5[LBL] +- 0.4[QED+EW])e-10 (e+e- -based) and a_mu = (11,659,195.6
+- 5.8[had] +- 3.5[LBL] +- 0.4[QED+EW])e-10 (tau-based), where the errors
account for the hadronic, light-by-light (LBL) scattering and electroweak
contributions. The deviations from the measurement at BNL are found to be (22.1
+- 7.2 +- 3.5 +- 8.0)e-10 (1.9 sigma) and (7.4 +- 5.8 +- 3.5 +- 8.0)e-10 (0.7
sigma) for the e+e- and tau-based estimates, respectively, where the second
error is from the LBL contribution and the third one from the BNL measurement.Comment: 14 pages, 7 figures (to be submitted to Phys Lett B
Precision Measurements of the Semileptonic Charm Decays and
We investigate the decays and ,
where is or , using approximately 7 of data
collected with the CLEO III detector. We find . Fits to
the kinematic distributions of the data provide parameters describing the form
factor of each mode. Combining the form factor results and gives
.Comment: 5 pages, 2 figures, talk given at DPF'04, UC Riverside, C
Dynamical breakdown of Abelian gauge chiral symmetry by strong Yukawa interactions
We consider a model with anomaly-free Abelian gauge axial-vector symmetry,
which is intended to mimic the standard electroweak gauge chiral SU(2)_L x
U(1)_Y theory. Within this model we demonstrate: (1) Strong Yukawa interactions
between massless fermion fields and a massive scalar field carrying the axial
charge generate dynamically the fermion and boson proper self-energies, which
are ultraviolet-finite and chirally noninvariant. (2) Solutions of the
underlying Schwinger-Dyson equations found numerically exhibit a huge
amplification of the fermion mass ratios as a response to mild changes of the
ratios of the Yukawa couplings. (3) The `would-be' Nambu-Goldstone boson is a
composite of both the fermion and scalar fields, and it gives rise to the mass
of the axial-vector gauge boson. (4) Spontaneous breakdown of the gauge
symmetry further manifests by mass splitting of the complex scalar and by new
symmetry-breaking vertices, generated at one loop. In particular, we work out
in detail the cubic vertex of the Abelian gauge boson.Comment: 11 pages, REVTeX4, 10 eps figures; additional remarks and references
added; version published in Phys. Rev.
A theory driven analysis of the effective QED coupling at
An evaluation of the effective QED coupling at the scale M_Z is presented. It
employs the predictions of perturbative QCD for the cross section of electron
positron annihilation into hadrons up to order \alpha_s^2, including the full
quark mass dependence, and of order \alpha_s^3 in the high energy region. This
allows to predict the input for the dispersion relations over a large part of
the integration region. The perturbative piece is combined with data for the
lower energies and the heavy quark thresholds. The result for the hadronic
contribution to the running of the coupling \Delta\alpha^{(5)}_{\rm
had}(M_Z^2)= (277.5 \pm 1.7)\times 10^{-4} leads to
(\alpha(M_Z^2))^{-1}=128.927 \pm 0.023. Compared to previous analyses the
uncertainty is thus significantly reduced.Comment: 9 pages (Latex); minor error in result for charm threshold region
fixed; final result unchange
New results in rho^0 meson physics
We compare the predictions of a range of existing models based on the Vector
Meson Dominance hypothesis with data on e^+ e^- -> pi^+ pi^$ and e^+ e^- ->
mu^+ mu^- cross-sections and the phase and near-threshold behavior of the
timelike pion form factor, with the aim of determining which (if any) of these
models is capable of providing an accurate representation of the full range of
experimental data. We find that, of the models considered, only that proposed
by Bando et al. is able to consistently account for all information, provided
one allows its parameter "a" to vary from the usual value of 2 to 2.4. Our fit
with this model gives a point-like coupling (gamma pi^+ \pi^-) of magnitude ~
-e/6, while the common formulation of VMD excludes such a term. The resulting
values for the rho mass and pi^+ pi^- and e^+e^- partial widths as well as the
branching ratio for the decay omega -> pi^+ pi^- obtained within the context of
this model are consistent with previous results.Comment: 34 pages with 7 figures. Published version also available at
http://link.springer.de/link/service/journals/10052/tocs/t8002002.ht
Simple quantum cosmology: Vacuum energy and initial state
A static non-singular 10-dimensional closed Friedmann universe of Planck
size, filled with a perfect fluid with an equation of state with w = -2/3, can
arise spontaneously by a quantum fluctuation from nothing in 11-dimensional
spacetime. A quantum transition from this state can initiate the inflationary
quantum cosmology outlined in Ref. 2 [General Relativity and Gravitation 33,
1415, 2001 - gr-qc/0103021]. With no fine-tuning, that cosmology predicts about
60 e-folds of inflation and a vacuum energy density depending only on the
number of extra space dimensions (seven), G, h, c and the ratio between the
strength of gravity and the strength of the strong force. The fraction of the
total energy in the universe represented by this vacuum energy depends on the
Hubble constant. Hubble constant estimates from WMAP, SDSS, the Hubble Key
Project and Sunyaev-Zeldovich and X-ray flux measurements range from 60 to 72
km/(Mpc sec). With a mid-range Hubble constant of 65 km/(Mpc sec), the model in
Ref. 2 predicts Omega-sub-Lambda = 0.7Comment: To be published in General Relativity and Gravitation, Vol. 37, May
2005. 5 pages, no figure
Одномоментная коррекция врожденной брахиметатарзии у подростков и пациентов молодого возраста
Introduction. Brachymetatarsia is a relatively rare abnormal shortening of metatarsal bone with female predominance. No consensus exists about the ideal surgical treatment for this condition while the two common strategies are gradual lengthening using external fixation and acute one stage lengthening. We describe the surgical technique of acute lengthening using iliac bone graft and report our results. Materials and Methods. Twelve patients (11 females, one male) with 14 short metatarsals were treated in our hospital over a 12-year period. The mean age was 17.4 years (range 14-28 years). Treatment protocol included metatarsal osteotomy, lengthening of extensor tendon and percutaneous tenotomy of the flexor tendon at the level of affected MP joint. Autologous iliac bone graft was inserted after elongation of the metatarsal by distraction through the osteotomy site and fixed using Kirshner wire. Results. Average metatarsal shortening was 13mm (range, 11-18 mm). The metatarsal length gained was an average of 12mm (range, 11-15 mm). Uneventful bone union was achieved in all cases after six weeks. At the end of treatment, the normal cascade of the metatarsal heads (metatarsal parabola) had been restored in 11 of the 14 metatarsals treated. There were no wound complications or pin tract infections around the wire. All but one patient were satisfied with the cosmetic appearance of the foot. Conclusion. Based on our experience, acute metatarsal lengthening using an iliac autugraft is a reliable and effective treatment method for congenital brachymetatarsia in adolescents and young adults.Level of Evidence: Level IV Case series.Введение. Брахиметатарзия является относительно редкой патологией аномального укорочения плюсневых костей, наиболее часто встречающейся у женщин. В настоящее время отсутствует консенсус в отношении идеального хирургического метода лечения данной деформации, и существуют две общепризнанные стратегии лечения: постепенное удлинение с использованием чрескостного остеосинтеза и одномоментное удлинение с применением аутотрансплантата. Авторы описывают хирургическую технику и приводят свои результаты выполнения одномоментной процедуры удлинения с использованием аутотрансплантата из гребня подвздошной кости. Материал и методы. За 12-летний период в клинике были прооперированы 12 пациентов (11 женщин, 1 мужчина) с укорочениями 14 плюсневых костей. Средний возраст пациентов — 17,4 лет (от 14 до 28 лет). Протокол лечения включал остеотомию плюсневых костей, удлинение сухожилия разгибателя и чрезкожную тенотомию сухожилия сгибателя на уровне деформированного пястно-фалангового сустава. Аутотрансплантат из гребня подвздошной кости помещали в область остеотомии после дистракции плюсневой кости и фиксировали спицами Киршнера. Результаты. Средняя величина укорочения плюсневых костей составляла 13 мм (в диапазоне от 11 до 18 мм). Средняя величина достигнутого удлинения составила 12 мм (в диапазоне от 11 до 15 мм). Костное сращение без осложнений у всех пациентов наблюдали через шесть недель. В результате лечения было восстановлено нормальное анатомическое соотношение головок плюсневых костей (плюсневая парабола) у 11 из 14 плюсневых костей. Авторы не наблюдали случаев осложнения заживления хирургической раны или инфекции в области введения спиц. За исключением одного все пациенты были удовлетворены эстетическим внешним видом стопы. Заключение. Исходя из опыта авторов, одноэтапное удлинение плюсневых костей с применением аутотрансплантата из подвздошной кости является надежным и эффективным методом лечения врожденной брахиметатарзии у подростков и пациентов молодого возраста. Уровень доказательности: IV, серия клинических наблюдений
On the theoretical uncertainties in the muon anomalous magnetic moment
I present a fairly detailed discussion of various contributions to the
anomalous magnetic moment of the muon a_mu. I try to give an unbiased
evaluation of the validity of the SM prediction for this quantity and to point
out some delicate issues involved in its calculation. I conclude that the
theory uncertainties in the SM prediction for the muon anomalous magnetic
moment are underestimated and a great deal of work will be required to reduce
these uncertainties to the level required by experiment.Comment: 12 pages, revte
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