Search results for " singularity"
showing 10 items of 203 documents
Triangle singularity enhancing isospin violation in $D_s^ + \to {\pi ^ + }{\pi ^0}{f_0}(980)$ and $\overline B _s^0 \to J/\psi {\pi ^0}{f_0}(980)$ de…
2019
We investigate isospin violation in the and reactions, which proceed via a triangle mechanism. We show that the mechanism develops a singularity around the π 0 f 0 (980) or π 0 a0 (980) invariant mass of 1420 MeV where the π 0 f 0 and π 0 a0 decay modes are magnified and also the ratio of π 0 f0 to π 0 a0 production, stressing the role of the triangle singularities as a factor to enhance isospin violation. The measurement of these reactions would bring further information into the role of triangle singularities in isospin violation and the a 0 – f 0 mixing in particular and shed further light into the nature of the low lying scalar mesons.
Calculation of theO(? s 2 ) parity-violating structure functions in $$e^ + e^ - \to q\bar qg$$
1986
We calculate the two nonvanishingO(αs2) parity-violating structure functions that contribute to\(e^ + e^ - \xrightarrow{{\gamma ,Z}}q\bar qg\). We discuss how these can be measured. We work with massless quarks and gluons and use dimensional regularization to regularize ultra-violet and infrared singularities. We carefully discuss how to deal withγ5 in the dimensional regularization scheme when infrared singularities are present.
Study of the possible role of triangle singularities in ${B^ - }\, \to {D^{*0}}{\pi ^ - }{\pi ^0}\eta $ and ${B^ - }\, \to {D^{*0}}{\pi ^ - }{\pi ^ +…
2019
Studying the effects of triangle singularities in hadronic processes is of the utmost importance since they can originate peaks that may wrongfully be associated with resonances. In this work, the role of the triangle mechanism in the decays and is explored. Here, the singularity appears when B- decays into , K *0 decays into K + through pion emission, and K - K + fuse together forming either the a 0 (980) or f 0 (980) which then decays into π 0 η or π+ π – , respectively. As a result, the K * K + K - loop generates a peak in the invariant mass of π - a 0 or π - f 0 around 1420 MeV. The branching ratios that come from this peak are and , which are well within the measurable range. Thus, thi…
Deforming D-brane models on T6/(Z2×Z2M) orbifolds
2016
We review the stabilisation of complex structure moduli in Type IIA orientifolds, especially on with discrete torsion, via deformations of orbifold singularities. While D6-branes in SO(2N) and USp(2N) models always preserve supersymmetry and thus give rise to flat directions, in an exemplary Pati-Salam model with only U(N) gauge groups ten out of the 15 deformation moduli can be stabilised at the orbifold point.
The extensions of gravitational soliton solutions with real poles
1998
We analyse vacuum gravitational "soliton" solutions with real poles in the cosmological context. It is well known that these solutions contain singularities on certain null hypersurfaces. Using a Kasner seed solution, we demonstrate that these may contain thin sheets of null matter or may be simple coordinate singularities, and we describe a number of possible extensions through them.
Integrability of J f and 1∕J f
2013
In this chapter we study the optimal degree of integrability of J f and 1∕J f for mappings of finite distortion. As an application of our estimates we show that some sets are removable singularities for mappings with exponentially integrable distortion.
Finitely determined singularities of ruled surfaces in 3
2009
AbstractWe study local singularities of ruled surfaces in 3. We show that any map germ f : (2, 0) → (3, 0) with a simple singularity is -equivalent to a ruled surface. Moreover, we give a topological classification of -finitely determined singularities of ruled surfaces and show that there are just eleven topological classes.
Infrared singularities in one-loop amplitudes
2010
In this talk we discuss a purely numerical approach to next-to-leading order calculations in QCD. We present a simple formula, which provides a local infrared subtraction term for the integrand of a one-loop amplitude. In addition we briefly comment on local ultraviolet subtraction terms and on the required deformation of the contour of integration.
From stringy particle physics to moduli stabilisation and cosmology
2016
Intersecting D6-branes provide a geometrically intuitive road to stringy particle physics models, where D6-branes stuck at orbifold singularities can lead to the stabilisation of deformation moduli, and the QCD axion can arise from the open string sector in a very constrained way compared to pure field theory. We demonstrate this interplay of different physical features here through an explicit model.
A Comment on form-factor mass singularities in flavor changing neutral currents
1991
Flavor-changing effective verticesq l q h V 0, whereV 0 represents a neutral gauge boson (γ,Z 0,g), involving a heavy external quark, are discussed within the standard model at one-loop level and second-order approximation in external momenta and masses: the logarithmic singular terms in the form factors at vanishing mass of the internal quark in the loop have to be replaced by pieces coming from next order in external momenta. Implications in theb→d+X penguin transitions are commented.