arXiv subjects

Yumian Su

Publications and source records attributed to Yumian Su.

5 recordsLinked to original sources

arXiv2015

Narrowband biphoton generation in the group delay regime

We study narrow-band biphoton generation from spontaneous four-wave mixing with electromagnetically induced transparency in a laser cooled atomic ensemble. We compare two formalisms in the interaction and Heisenberg pictures, and find that they agree in the low gain regime but disagree in the high gain regime. We extend both formalisms accounting the non-uniformity in atomic density and the driving laser fields. We find that for a fixed optical depth and a weak and far-detuned pump laser beam, the two-photon waveform is independent of the atomic density distribution. However, the spatial profiles of the two driving laser beams have significant effects on the biphoton temporal waveform. We predict that waveform shaping in time domain can be achieved by controlling the spatial profiles of the driving laser fields.

quant-ph↗

arXiv1997

Tevatron Constraints on Topcolor-Assisted Technicolor

We study the constraints on models of topcolor-assisted technicolor arising from measurements of high-$E_T$ jets and high-mass lepton pairs at the Tevatron collider. Existing data can eliminate models that have appeared in the literature.

hep-ph↗

arXiv1996

$B \to X_s μ^+ μ^-$ in Technicolor with Scalars

We compute the flavor changing neutral current process $B \to X_s μ^+ μ^-$ in technicolor models with scalars. We find that the branching ratio can be enhanced relative to that of the Standard Model by as much as 60%. The full parameter space of the model is consistent with the present CLEO and CDF exclusive limits. However, the viability of the model could soon be tested since the decay signals are expected to be observed in the next few years with the upgraded CLEO detector and in the CDF Run II.

hep-ph↗

arXiv1996

$Z\to b\bar b$ in $U(1)_R$ Symmetric Supersymmetry

We compute the one-loop corrections to the $Z \to b\bar{b}$ vertex in the $U(1)_R$ symmetric minimal supersymmetric extension of the standard model. We find that the predicted value of $R_b$ is consistent with experiment if the mass of the lighter top squark is no more than 180 GeV. Furthermore, other data combines to place a lower bound of 88 GeV on the mass of the light top squark. A top squark in this mass range should be accessible to searches by experiments at FNAL and LEP.

hep-ph↗

arXiv1994

b \rightarrow s γAND Z \rightarrow b \overline{b} IN TECHNICOLOR WITH SCALARS

We consider the radiative decay $b\rightarrow s γ$, and the correction to the $Zb\overline{b}$ vertex in technicolor models with scalars. In these models, the scalar develops a vacuum expectation value when the technifermions condense, and the ordinary fermions develop masses via Yukawa couplings. Since the symmetry breaking sector involves both a fundamental scalar doublet and an isotriplet of composite scalars (the technipions), the phenomenology associated with the charged scalars is similar to that found in a type-I two-Higgs doublet model. We show that the correction to the $Zb\overline{b}$ vertex is small over the allowed parameter space of the model in the two limits that we consider, and that there can be large, potentially observable, contributions to the $b\rightarrow s γ$ branching fraction.

hep-ph↗