High Et Jet Production

A review is presented on studies of high $E_T$ jet production and production of photon, $W$ and $Z$ associated with jets from the HERA and Tevatron experiments. Such studies have been used to examine the Standard Model (SM) in the area of the strong interaction, Quantum Chromodynamics, at highest energies currently attainable in collider experiments, to extract values of the coupling of the strong interaction, to determine the parton distribution functions in the proton, and to provide constraints on SM processes that constitute background to the Higgs boson and new physics searches. Some of them are also directly sensitive to the presence of physics beyond the SM. Future prospects for results from the LHC experiments are discussed.Comment: 8 pages, 16 figures, to be appeared in the proceedings for XXIX Physics in Collision, International Symposium in Kobe, Japan, August 30 - September 2, 200

Jet Physics at CDF

Recent results on jet physics at the Fermilab Tevatron $p\bar p$ collider from the CDF Collaboration are presented. The main focus is put on results for the inclusive jet and dijet, $b\bar b$ dijet, $W/Z+$jets and $W/Z+b$-jets production.Comment: Proceedings for ISMD 200

Vector Boson + Heavy Flavor Jets Production at the Tevatron

Recent measurements on the vector boson plus heavy-flavor jets production by the CDF and D0 experiments are presented in comparisons with recent theoretical predictions. Good understanding of such processes is important to improve our understanding of QCD and also to enhance the potential to search for yet-to-be-discovered new physics phenomena which lead to similar final states.Comment: Contribution to the Proceedings of the 34th International Conference on High Energy Physics; 4 pages, 4 figure

High Sensitivity Anti-Neutrino Detection by KamLAND

Electron anti-neutrinos from nuclear power reactors have been observed by KamLAND. Data from 0.16 kton-year exposure (145.1 live days) indicates disappearance of electron anti-neutrinos at 99.95% C.L. in the energy range 2.6 MeV < E < 8.0 MeV. Considering two-flavor neutrino oscillation with CPT invariance, the only remaining solution to the solar neutrino problem is the Large Mixing Angle (LMA) solution. In addition a 0.28kton-year exposure (185.5 live days) was searched for electron anti-neutrinos in the energy range 8.3 MeV < E < 14.8 MeV. No candidate events were found with expected background of 1.1 +- 0.4 events. Assuming that the origin of electron anti-neutrinos in this energy region comes from 8B solar electron neutrinos, we find an upper limit of neutrino to anti-neutrino conversion probability of 0.00028.Comment: 8 pages, 6 Postscript figures, Proceedings of Moriond EW0

Measurement of the flux and zenith-angle distribution of upward through-going muons in Kamiokande II+III

The flux of upward through-going muons of minimum (mean) threshold energy > 1.6 (3.0) GeV is measured, based on a total of 372 events observed by the Kamiokande II+III detector during 2456 detector live days. The observed muon flux was (1.94+-0.10(stat.)+0.07-0.06(sys.))*10^-13 /cm^2/s/sr, which is compared to an expected value of (2.46+-0.54(theo.))*10^-13/cm^2/s/sr. The observation is in agreement with the prediction within the errors. The zenith angle dependence of the observed upward through-going muons supports the previous indication of neutrino oscillations made by Kamiokande using sub- and multi-GeV atmospheric neutrino events.Comment: 9 pages with 3 eps figures, uses psfig.sty and revtex, submitted to PR

Correlation functions and renormalization in a scalar field theory on the fuzzy sphere

We study renormalization in a scalar field theory on the fuzzy sphere. The theory is realized by a matrix model, where the matrix size plays the role of a UV cutoff. We define correlation functions by using the Berezin symbol identified with a field and calculate them nonperturbatively by Monte Carlo simulation. We find that the 2-point and 4-point functions are made independent of the matrix size by tuning a parameter and performing a wave function renormalization. The results strongly suggest that the theory is nonperturbatively renormalizable in the ordinary sense.Comment: 22 pages, 11 figures, published versio

Strong-coupling approach to antiferromagnetic ordering driven by paramagnetic pair-breaking in d-wave superconducting phase

The field-induced antiferromagnetic (AFM) ordering in the $d_{x^2-y^2}$-paired superconducting phase, which has been recently found in the weak-coupling approach as a basic mechanism due to the Pauli paramagnetic pair-breaking (PPB) in relation to the high-field behaviors in CeCoIn_5, is studied in the strong-coupling approach taking account of the electron correlation. Applying the fluctuation-exchange (FLEX) approximation to the two-dimensional Hubbard model including the Zeeman term, it is shown that the PPB-induced AFM ordering in the superconducting (SC) phase and the first order SC transition on H_{c2}(T) are realized in the strong-coupling approach as well as those in the weak-coupling model, and that the AFM ordering is affected by the quasiparticle renormalization and the amplitude of the SC order parameter. This AFM ordering may appear in a wide range of materials close to an AFM quantum critical point (QCP).Comment: 24 pages, 9 figures, revisions are made mainly in section 6, title is changed slightl

Entropic Quantum Machine

We study nanomachines whose relevant (effective) degrees of freedom f >> 1 but smaller than f of proteins. In these machines, both the entropic and the quantum effects over the whole system play the essential roles in producing nontrivial functions. We therefore call them entropic quantum machines (EQMs). We propose a systematic protocol for designing the EQMs, which enables a rough sketch, accurate design of equilibrium states, and accurate estimate of response time. As an illustration, we design a novel EQM, which shows two characteristic shapes. One can switch from one shape to the other by changing temperature or by applying a pulsed external field. We discuss two potential applications of this example of an EQM.Comment: 9 pages, 4 figures; Several typos are fixe

Non-negligible collisions of alkali atoms with background gas in buffer-gas-free cells coated with paraffin

We measured the rate of velocity-changing collisions (VCCs) between alkali atoms and background gas in buffer-gas-free anti-relaxation-coated cells. The average VCC rate in paraffin-coated rubidium vapor cells prepared in this work was $1 \times 10^{6}$ s$^{-1}$, which corresponds to $\sim 1$ mm in the mean free path of rubidium atoms. This short mean free path indicates that the background gas is not negligible in the sense that alkali atoms do not travel freely between the cell walls. In addition, we found that a heating process known as "ripening" increases the VCC rate, and also confirmed that ripening improves the anti-relaxation performance of the coatings.Comment: 5 pages, 4 figure

Coupled k-space structure of dd-wave superconducting and magnetic orders induced by paramagnetic pair-breaking effect

We theoretically investigate k-space structures of $d_{x^2-y^2}$-wave superconducting (SC) and spin-density-wave (SDW) orders in their coexistent phase induced by a paramagnetic pair-breaking (PPB) effect in relation to the high field and low temperature (HFLT) SC phase in CeCoIn$_5$. It is shown that, in k-space, the SDW order develops near the gap nodes where the SC order is suppressed by PPB, and the nesting condition for the SDW ordering is satisfied. By comparing the results in the $d_{x^2-y^2}$-wave SC model and those in an artificial model with no sign change of the gap function in k-space with each other, it is shown that the $d_{x^2-y^2}$-wave SC and SDW orders are enhanced altogether in k-space due to the sign change of the $d_{x^2-y^2}$-wave gap function there, and that this mutual enhancement largely stabilizes the coexistence of these orders in real space. It is also discussed that the field dependence of a SDW moment can be affected by the k-space structure of these orders, which is dependent on the curvature of the Fermi surface.Comment: 9 pages, 4 figure