118491865
The CDF dijet excess and Z'cs coupled to the second generation quarks
Recently the CDF collaboration has reported the excess in the dijet invariant-mass distribution of the Wjj events, corresponding to a significance of 3.2 standard deviations. Considering the lack of similar excesses in the $\gamma jj$ and $Z jj$ events yet, we propose a new Z' model: Z' couples only to the second generation quarks. Single production of $\zsc$ as well as associated production with $W,\gamma, Z$ are mainly from the sea quarks. Only $W Z'$ production has additional contribution from one valence quark and one sea quark, which is allowed by CKM mixing. We found that if the new gauge coupling is large enough, marginally permitted by perturbativity, this new model can explain the observed CDF $Wjj$ anomaly as well as the lack of $\gm jj$ and $Z jj$ anomalies. Vanishing coupling of Z'-b-b protects this model from the constraint of p pbar ->WH -> l\nu b \bar{b}.
17539215
Implications of the recent CERN LEP data on nonuniversal interactions with the precision electroweak tests
We explore the nonuniversal interaction effects in terms of the precision variables epsilons with the recent CERN LEP data reported by the Electroweak Working Group. The epsilon variables with the nonuniversal interactions are calculated and constrained by the experimental ellipses in the {epsilon}{sub 1}{endash}{epsilon}{sub b}, {epsilon}{sub 2}{endash}{epsilon}{sub b}, and {epsilon}{sub 3}{endash}{epsilon}{sub b} planes. We find that the new data enable us to make a stringent test on the correction to Z{r_arrow}b{bar b} vertex. The {epsilon}{sub b} variable is sensitive to the Zb{bar b} couplings and thus plays a major role to give constraints on the nonuniversal interaction effects. Upon imposing the new data on {epsilon}{sub b}, we have the allowed range of the model parameter {kappa}{sub L}=0.0063{plus_minus}0.0030 at 1-{sigma} level with m{sub t}=175 GeV. Along with the minimal contact term, we predict the new physics scale {Lambda}{approximately} 1.6 TeV. By combining the experimental results from all planes we obtain the allowed range of {kappa}{sub L}: 0.003{lt}{kappa}{sub L}{lt}0.010 at 95{percent} C.L. {copyright} {ital 1997} {ital The American Physical Society}
16221979
POLARIZATION EFFECTS ON THE E+E- W+W- PROCESS WITH LARGE EXTRA DIMENSIONS
Abstract We study large extra dimension effects on the polarizations of the W pair and electron beam at the e + e − → W + W − process. It is shown that the measurements of the cross section for transversely polarized W pair with the right-handed electron beam remarkably enhance the possibilities to see the low scale quantum gravity effects. Higher Linear Collider bounds on the string scale in this model can be obtained by using the left-handed electron beam.
14611917
Polarization effects on W boson pair productions with the extra neutral gauge boson at the e^+ e^- Linear Collider
We perform the comprehensive analysis of the polarization effects on the e^+e^- -> W^+W^- process in the presence of the extra neutral gauge boson at the LC energies. Consideration of the polarizations of the produced W bosons and the beam polarizations provides substantial enhancements of the sensitivity to the Z-Z' mixing angles in various models and the asymmetry variables also give the strict constraints on the mixing angles. We find that the \chi-model and the left-right model get the strict constraint from \sigma_{LL}^{unpol} while the \psi-model and the \eta-model from the beam polarization asymmetry.
16963420
Evolution equation for the heavy quark distribution function in the parton model approach
We explore the perturbative QCD corrections to the inclusive semileptonic decays of $B$ mesons. In inclusive $B$ decay processes the parton picture works well and the scaling feature manifests because the mass of $b$ quark is larger than the QCD scale. Due to this property, the decay rate may be expressed by a single structure function describing the light-cone distribution of $b$ quark apart from the kinematic factor. We derive a $q^2$ evolution equation for the distribution function, which violates the scaling property through the Altarelli-Parisi type approach. The evolution equation is numerically solved and its phenomenological implications are also discussed.
15426025
Large extra dimension effects on the spin configuration of the top quark pair at e + e − colliders
Large extra dimension effects on the spin configuration of the top quark pair at the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{t}$ process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from standard model (SM) predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin states of the top quark pair, which vanish in the SM; they weaken the pure dominance of the processes, the up-down (down-up) spin states for the left-handed (right-handed) beam. In addition it is shown that the angular cut $\ensuremath{-}0.5l\mathrm{cos}\ensuremath{\theta}l0$ is very effective to determine the sign of the quantum gravity corrections.
17221530
Dileptons from decay of vector mesons hadronized from a quark-gluon plasma
We present a simple model for the dimuon production from the decay of vector mesons which are hadronized from a baryon-free quark-gluon plasma. Continuous decay of vector mesons in the medium is known to enhance the dimuon production and in our model we can estimate the total yield of dimuons decayed from vector mesons through the rate equations for the number of vector mesons of interest. Muon pair production critically depends on the time duration of both the mixed and hadronic phases. Results are discussed in view of possible measurements in experiments.
17654907
= 5, 6 superconformal Chern-Simons theories and M2-branes on orbifolds
We explore further our recent generalization of the = 4 superconformal Chern-Simons theories of Gaiotto and Witten. We find and construct explicitly theories of enhanced = 5 or 6 supersymmetry, especially = 5, Sp(2M) ? O(N) and = 6, Sp(2M) ? O(2) theories. The U(M) ? U(N) theory coincides with the = 6 theory of Aharony, Bergman, Jafferis and Maldacena (ABJM). We argue that the = 5 theory with Sp(2N) ? O(2N) gauge group can be understood as an orientifolding of the ABJM model with U(2N) ? U(2N) gauge group. We briefly discuss the Type IIB brane construction of the = 5 theory and the geometry of the M-theory orbifold.
119961422
Search for collective flow in relativistic heavy-ion collisions using transverse momentum spectra of emitted hadrons☆
122366381
Collective flow model for the pion transverse momentum spectra from relativistic nuclear collisions at CERN
The transverse momentum spectra for pions observed by WA80 and NA35 collaborations are analysed within a fireball model with collective isentropic expansion and a realistic freeze-out criterion. By varing the initial state of the fireball, an excellent fit to the data is achieved for the whole measured range ofPT. Slight differences in the data for the spectral slopes from central and pheripheral collisions originate in our model from the difference in the size of the fireball and in the number of participating nucleons in central and peripheral collisions. Using additional information from two-pion correlations, we can extrapolate our model back from the freeze-out point (determined from the spectra) to the initial state; we find that an initial energy density of 1.5–2GGeV/fm3 is sufficient to explain the data from central O+Au collisions at 200A GeV.
10623913
= 4 Superconformal Chern-Simons theories with hyper and twisted hyper multiplets
We extend the = 4 superconformal Chern-Simons theories of Gaiotto and Witten to those with additional twisted hyper-multiplets. The new theories are generically linear quiver gauge theories with the two types of hyper-multiplets alternating between gauge groups. Our construction includes the Bagger-Lambert model of SO(4) gauge group. A family of abelian theories are identified with those proposed earlier in the context of the M-crystal model for M2-branes probing (2/n)2 orbifolds. Possible extension with non-abelian BF couplings and string/M-theory realization are briefly discussed.