arXiv subjects

Jake Lee

Publications and source records attributed to Jake Lee.

31 records · Page 2Linked to original sources

arXiv2005

Lepton Flavor Violation as a Probe of Quark-Lepton Unification

The recent measurements of the solar neutrino mixing angle theta_{sol} and the Cabibbo mixing angle theta_C reveal a surprising relation, theta_{sol}+theta_C ~ pi/4. Interpreting this empirical relation as a support of the quark-lepton unification, we find that the PMNS mixing matrix can be decomposed into a CKM-like matrix and maximal mixing matrices, which can give profound implications on the quark-lepton unification. We explore a possibility to probe the implication of quark-lepton unification by considering the relative sizes of branching ratios for the lepton flavor violating radiative decay processes, l_i-->l_j gamma, in the context of the supersymmetric standard model with heavy right-handed Majorana neutrinos.

hep-ph↗

arXiv2002

Measurement of $|V_{ub}|$ in semi-inclusive charmless $B \to πX$ decays

We study semi-inclusive charmless decays $B \to πX$, where $X$ does not contain a charm (anti)quark. The mode $\bar B^0 \to π^- X$ turns out to be be particularly useful for determination of the CKM matrix element $|V_{ub}|$. We present the branching ratio (BR) of $\bar B^0 \to π^- X$ as a function of $|V_{ub}|$, with an estimation of possible uncertainty. The BR is expected to be an order of $10^{-4}$.

hep-ph↗

arXiv2002

A study of semi-inclusive charmless $B \to πX$ decays

We study semi-inclusive charmless decays $B \to πX$ in detail, such as $\bar B^0 \to π^{\pm (0)} X$, $B^0 \to π^{\pm (0)} X$, $B^{\pm} \to π^{\pm (0)} X$, where $X$ does not contain a charm (anti)quark. We find that the process $\bar B^0 \to π^- X$ ($B^0 \to π^+ X$) can be particularly useful for determination of the CKM matrix element $|V_{ub}|$. We calculate and present the branching ratio (BR) of $\bar B^0 \to π^- X$ as a function of $|V_{ub}|$, with an estimate of possible uncertainties. It is expected that the BR is an order of $10^{-4}$. Our estimation indicates that one can phenomenologically determine $|V_{ub}|$ with reasonable accuracy by measuring the BR of $\bar B^0 \to π^- X$ ($B^0 \to π^+ X$).

hep-ph↗

arXiv2001

Test of Factorization Hypothesis from Exclusive Non-leptonic B decays

We investigate the possibility of testing factorization hypothesis in non-leptonic exclusive decays of B-meson. In particular, we considered the non factorizable \bar{B^0} -> D^{(*)+} D_s^{(*)-} modes and \bar{B^0} -> D^{(*)+} (π^-, ρ^-) known as well-factorizable modes. By taking the ratios BR(\bar{B^0}-> D^{(*)+}D_s^{(*)-})/BR(\bar{B^0}-> D^{(*)+}(π^-,ρ^-)), we found that under the present theoretical and experimental uncertainties there's no evidence for the breakdown of factorization description to heavy-heavy decays of the B meson.

hep-ph↗

arXiv2000

Measurement of |V_{ub}/V_{cb}| (and |V_{ub}|) in Exclusive Nonleptonic Decays, \bar{B}^0 --> D_s^{()-}(π^+,ρ^+) and \bar{B}^0 --> D_s^{()-}D^{(*)+}

We have studied extracting $|\vub/\vcb|$ by calculating the ratios ${\cal B}(\bar{B}^0\to D_s^{(*)-}(π^+,ρ^+))/{\cal B}(\bar{B}^0\to D_s^{(*)-}D^{(*)+})$ including penguin effects within the factorization assumption. The ratios involving $\bar{B}^0\to D_s^-D^{+}$ mode have considerable penguin corrections ($\sim 15%$ at the amplitude level), but those involving $\bar{B}^0\to D_s^-D^{*+}$ mode have relatively small penguin corrections. On the other hand, the $\bar{B}^0\to D_s^-D^{+}$ mode has smaller form-factor dependance. Therefore, these ratios complement each other in measuring $\vub/\vcb$. The theoretical uncertainty from the hadronic form factors in our method is at the level of 15%, which is comparable to the model-dependence uncertainty of about 20% in the measurement of $| \vub/\vcb |$ from the exclusive semileptonic B decays. Using the newest upper limit on $B\to D_s π$ decay from CLEO, our method sets an upper limit $| \vub/\vcb | < 0.13$ which is very close to the measured values from the semileptonic B decays. We also discuss the possible breaking of factorization assumption.

hep-ph↗

arXiv1999

Search for New Physics in the Semileptonic D_{l4} Decays, D->K πl ν

New physics effects through the direct CP violation and the decay rate change are investigated in the semileptonic $D_{l4}$ decays, $D^\pm\to Kπl^\pm ν$, by including a scalar-exchange interaction with a complex coupling. In the decay process, we included various excited states as intermediate states decaying to the final hadrons, $K+π$, and found that among the intermediate states only the lowest state ($K^*$) is dominant and the other higher excited states are negligible, contrary to the $B_{l4}$ decays. We also obtained constraints on the new complex coupling within the multi-Higgs doublet model and the scalar leptoquark models.

hep-ph↗

arXiv1999

CP Violation in the Semileptonic B_{l4} (B^\pm -> pi^+ π^- l^\pm ν) Decays

Direct CP violations in $B_{l4}$ decays ($B^\pm \to π^+π^- l^\pm ν_l$) are investigated within the Standard Model (SM) and also in its extensions. In the decay processes, we include various excited states as intermediate states decaying to the final hadrons, $π^+ + π^-$. The CP violation within the SM is induced by the interferences between intermediate resonances with different quark flavors. As extensions of the SM, we consider CP violations implemented through complex scalar-fermion couplings in the multi-Higgs doublet model and the scalar-leptoquark models. We calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry can be measured at $1σ$ level with about $10^9$ $B$-meson pairs in the SM case and $10^3$--$10^7$ pairs in the extended model case, for maximally-allowed values of CP-odd parameters in each case.

hep-ph↗

arXiv1998

CP Violation in the Semileptonic $B_{l4}$ (B->D πl ν) Decays: A Model Independent Analysis

CP violation from physics beyond the Standard Model is investigated in $B_{l4}$ decays: $B\to Dπl\barν_l$. The semileptonic $B$-meson decay to a $D$-meson with an emission of single pion is analyzed with heavy quark effective theory and chiral perturbation theory. In the decay process, we include various excited states as intermediate states decaying to the final hadrons, $D+π$. The CP violation is implemented in a model independent way, in which we extend leptonic current by including complex couplings of the scalar sector and those of the vector sector in extensions of the Standard Model. With these complex couplings, we calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that the optimal asymmetry is sizable and can be detected at $1σ$ level with about $10^6$-$10^7$ $B$-meson pairs, for some reference values of new physics effects.

hep-ph↗

arXiv1998

CP Violation in the Semileptonic $B_{l4}$ ($B->D πl ν$) Decays: Multi-Higgs Doublet Model and Scalar-Leptoquark Models

CP violation from physics beyond the Standard Model is investigated in $B_{l4}$ decays: $B\to Dπl\barν_l$. In the decay process, we include various excited states as intermediate states decaying to the final hadrons, $D+π$. We consider the semileptonic decay to a tau lepton family as well. The CP violation is implemented through complex scalar--fermion couplings in the multi-Higgs doublet model and scalar-leptoquark models beyond the Standard Model. With these complex couplings, we calculate the CP-odd rate asymmetry and the optimal asymmetry. We find that for $B_{τ4}$ decays the optimal asymmetry is sizable and can be detected at $1σ$ level with about $10^6$-$10^7$ $B$-meson pairs, for maximally-allowed values of CP-odd parameters in those extended models.

hep-ph↗

arXiv1998

CP Violation in the Cabbibo-suppressed Decay Tau->K Pi Nu_tau with Polarized Tau Leptons

CP violation from physics beyond the Standard Model (SM) is investigated in the Cabbibo-suppressed decay $τ\to Kπν_τ$ with polarized $τ$ leptons, to which both the ${\rm J}^{P}=1^-$ resonance $K^*$ and the $ J^{P}=0^+$ resonance $K^*_0$ contribute. In addition to the CP-odd rate asymmetry, $τ$ polarization enables us to construct three additional CP-odd polarization asymmetries that can be enhanced due to the interference between the $K^*$ and $K^*_0$, and whose magnitudes depend crucially on the $K^*_0$ decay constant, $f_{K^*_0}$. Taking a QCD sum rule estimate of $f_{K^*_0}=45$ MeV and the present experimental constraints on the CP-odd parameters into account, we estimate quantitatively the maximally-allowed values for the CP-odd rate and polarization asymmetries in the multi-Higgs-doublet (MHD) model and the scalar-leptoquark (SLQ) models consistent with the SM gauge symmetry where neutrinos are massless and left-handed as in the SM. We find that the CP-odd rate and polarization asymmetries are of a similar size for highly-polarized $τ$ leptons and, for their maximally-allowed values, CP violation in the MHD model and two SLQ models may be detected with about $10^6$ and $10^7$ $τ$'s at the $1σ$ level.

hep-ph↗

arXiv1998

T-Odd Gluon-Top-Quark Couplings at LHC

The T-odd top-quark chromoelectric dipole moment, $d_t$, is probed through top-quark-pair production via gluon fusion at the CERN LHC with the possibility of having polarized proton beams in account. At 1-$σ$ level, the typical CP-odd lepton energy and tensor correlations enable us to measure $Re(d_t)$ and $Im(d_t)$ up to the order of 10$^{-18}$ ($g_scm$) in the unpolarized case and the initial CP-odd gluon spin correlation allows us to probe $Im(d_t)$ up to the order of 10$^{-20}$ ($g_scm$) for $\sqrt{s}=14$ TeV and the integrated luminosity $L_{pp}=10 fb^{-1}$.

hep-ph↗

arXiv1997

T-odd Gluon-Top-Quark Effective Couplings at the CERN Large Hadron Collider

The T-odd top-quark chromoelectric dipole moment (tCEDM) is probed through top-quark-pair production via gluon fusion at the CERN Large Hadron Collider (LHC) by considering the possibility of having polarized protons. The complete analytic expressions for the tree-level helicity amplitudes of gg-> ttbar is also presented. For the derived analytic results we determine the 1-sigma statistical sensitivities to the tCEDM form factor for (i) typical CP-odd observables composed of lepton and anti-lepton momenta from t and tbar semileptonic decays for unpolarized protons, and (ii) a CP-odd event asymmetry for polarized protons by using the so-called Berger-Qiu (BQ) parametrization of polarized gluon distribution functions. We find that at the CERN LHC, the CP-odd energy and angular correlations can put a limit of 10^{-18} to 10^{-17} g_scm on the real and imaginary parts of the tCEDM, while the simple CP-odd event asymmetry with polarized protons could put a very strong limit of 10^{-20} g_scm on the imaginary part of the tCEDM.

hep-ph↗

arXiv1995

Large $p_T$ Hadroproduction of $Z$ as a Probe of Gluon Distribution inside Proton

The transverse momentum distribution of single vector boson production at hadron colliders provides useful ways of testing the Standard Model and searching new physics beyond the Standard Model. We study large $p_{_T}$ hadroproduction of $Z$-boson as a probe of gluon distributions inside proton. We investigate how to get initial gluon-involving contributions, or how to subtract quark-quark (or -antiquark) contributions from total cross section. We also investigated the simultaneous measurement of the rapidity and the transverse momentum of the produced $Z$ boson, to obtain momentum fractions of initial partons. And we extracted relevant uncertainties involving in experimental and theoretical analyses. This large $p_{_T}$ hadroproduction of $Z$ can be used as constraints on analyses of global parton (gluon and quarks) distribution functions inside proton.

hep-ph↗