Large pTp_T Hadroproduction of ZZ 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.Comment: (a) 13 pages(LaTeX) + 1 figure ps file(3 pages):compressed, uuencoded (b) accepted by Phys.Lett.B. (c) some figures are combined and one is omitted. (d) conclusion part is included into abstrac

Nucleon Spin Structures from Lattice QCD: Flavor Singlet Axial and Tensor Charges

The flavor singlet axial and tensor charges of the nucleon are calculated in lattice QCD. We find $\Delta\Sigma=\Delta u+\Delta d+\Delta s=+0.638(54)-0.347(46)-0.109(30) = +0.18(10)$ for the axial charge and $\delta\Sigma=\delta u+\delta d+\delta s=+0.839(60)-0.231(55)-0.046(34) = +0.562(88)$ for the tensor charge. The result for the axial charge shows reasonable agreement with the experiment and that for the tensor charge is the first prediction from lattice QCD before experimental measurements.Comment: 10 pages, latex source-file, 5 figures as epsf-file, uses espcrc1.sty. Invited talk at the International Conference on Quark Lepton Nuclear Physics, 20-23 May 1997, Osaka, Japa

Third-generation leptoquark decays and collider searches

Collider searches for first-, second-, and third-generation scalar (S) or vector (V) leptoquarks (LQs) focus on the quark-lepton decay modes S,V -> q l. For SU(2)-doublet and -triplet leptoquarks with a sufficiently large splitting between the components, decays involving real W-boson emission (such as S_2^{(+5/3)} -> S_2^{(+2/3)} W^{+} and others) become possible and can change the patterns of leptoquark decays. For third-generation leptoquarks, where these mass splittings might be large, such modes could dominate certain leptoquark decays as they are (if kinematically allowed) guaranteed to be of order g^2 where g is the electroweak coupling. We calculate the decay rates for all such processes involving SU(2)-doublet and triplet, scalar and vector leptoquarks. Standard limits on mass splittings from precision electroweak measurements imply that only such decays involving SU(2)-doublet scalar LQs are likely kinematically possible.Comment: 13 pages, LaTeX, 2 separate postscript figure

Experimental constraints on the parameter space of the next-to-minimal supersymmetric standard model at LEP 2

We search for the neutral Higgs sector of the next-to-minimal supersymmetric standard model at LEP 2. At the tree level any experimental constraints on $\tan \beta$ cannot be set by the Higgs search at LEP 2 with $\sqrt{s}$ = 175 GeV, whereas at LEP 2 with $\sqrt{s}$ = 192 GeV $\tan \beta$ can be set by an experimental constraint. Furthermore the tree level parameter space of the model can be completely explored by the Higgs search at LEP 2 with $\sqrt{s}$ = 205 GeV. Radiative corrections both to the neutral Higgs boson masses and to the relevant couplings for the scalar Higgs productions give large contributions to the production cross sections of the scalar Higgs bosons at the tree level. The tree level situation at LEP 2 with $\sqrt{s}$ = 192 GeV as well as with $\sqrt{s}$ = 205 GeV can be drastically changed by these effects. We expect that a small region of the 1-loop level parameter space of the model via the scalar Higgs production can be explored by the Higgs search at LEP 2.Comment: 14 pages (3 figures are included

Strange and singlet form factors of the nucleon: Predictions for G0, A4, and HAPPEX-II experiments

We investigate the strange and flavor-singlet electric and magnetic form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. Isospin symmetry is assumed and the symmetry-conserving SU(3) quantization is employed, rotational and strange quark mass corrections being included. For the experiments G0, A4, and HAPPEX-II we predict the quantities $G^{0}_E + \beta G^{0}_M$ and $G^{\rm s}_E + \beta G^{\rm s}_M$. The dependence of the results on the parameters of the model and the treatment of the Yukawa asymptotic behavior of the soliton are investigated.Comment: 16 pages, 3 figures, Final version for publication in Eur. Phys. J.

Strange vector form factors of the nucleon in the SU(3) chiral quark-soliton model with the proper kaonic cloud

The strange vector form factors are evaluated in the range between $Q^2=0$ and Q^2=1\ \mbox{GeV}^2 in the framework of the SU(3) chiral quark-soliton model (or semi-bosonized SU(3) Nambu-Jona-Lasinio model). The rotational $1/N_c$ and $m_s$ corrections are taken into account up to linear order. Taking care of a proper Yukawa-tail of the kaonic cloud, we get \langle r^{2}\rangle^{\rm Sachs}_{s}=-0.095\; \mbox{fm}^2 and $\mu_s = -0.68\;\mu_N$. The results are compared with several different models.Comment: 27 pages with 8 figures. RevTeX and epsfig.sty are used. Submitted to Nucl. Phys.

Hyperon semileptonic decays and quark spin content of the proton

We investigate the hyperon semileptonic decays and the quark spin content of the proton $\Delta \Sigma$ taking into account flavor SU(3) symmetry breaking. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. As a result we predict the unmeasured decay constants, particularly for $\Xi^0 \to \Sigma^+$, which will be soon measured and examine the effect of the SU(3) symmetry breaking on the spin content $\Delta \Sigma$ of the proton. Unfortunately large experimental errors of $\Xi^-$ decays propagate in our analysis making $\Delta \Sigma$ and $\Delta s$ practically undetermined. We conclude that statements concerning the values of these two quantities, which are based on the exact SU(3) symmetry, are premature. We stress that the meaningful results can be obtained only if the experimental errors for the $\Xi$ decays are reduced.Comment: The final version accepted for publication in Phys. Rev. D. 18 pages, RevTex is used with 4 figures include

Dilepton Signatures of Family Non-Universal U(1)'

The supersymmetric models extending the minimal supersymmetric standard model (MSSM) by an additional Abelian gauge factor U(1)' in order to solve the mu problem do generically suffer from anomalies disrupting the gauge coupling unification found in the MSSM. The anomalies are absent if the minimal matter content necessitated by the mu problem is augmented with exotic matter species having appropriate quantum numbers. Recently, it has been shown that anomaly cancellation can also be accomplished by introducing family non-universal U(1)' charges and non-holomoprhic soft-breaking terms. We discuss collider signatures of anomaly-free family non-universal U(1)' model by analyzing dilepton production in future colliders. We find that, both at LHC and NLC, one can establish existence/absence of such a Z' boson by simply comparing the number of dilepton production events for electron, muon and tau lepton. The signal is free of the SM background.Comment: 12 pages, 4 figure

Folding and Aggregation of Designed Proteins

Studies of how protein fold have shown that the way protein clumps form in the test tube is similar to how proteins form the so-called ``amyloid'' deposits that are the pathological signal of a variety of diseases, among them the memory disorder Alzheimer's. Protein aggregation have traditionally been connected to either unfolded or native states. Inclusion body formation (disordered aggregation) has been assumed to arise from hydrophobic aggregation of the unfolded or denaturated states, while the amyloid fibrils (ordered aggregation) have been assumed to arise from native-like conformations in a process analogous to the polymerization of hemoglobin S. Making use of lattice-model simulations we find that both ordered and disordered aggregation arise from elementary structures which eventually build the folding nucleus of the heteropolymers, and takes place when some of the most strongly interacting amino acids establish their contacts leading to the formation of a specific subset of the native structure. These elementary structures can be viewed as the partially folded intermediates suggested to be involved in the aggregation of a number of proteins. These results have evolutionary implications, as the elementary structures forming the folding core of designed proteins contain the residues which are conserved among the members of homologous sequences.Comment: 10 pages, 2 colour ps figures and 1 b/w ps figur