We have measured invariant mass spectra of electron-positron pairs in the target rapidity region of 12GeV p+A reactions. We have observed a significant difference in the mass spectra below the ω meson between p+C and p+Cu interactions. The difference is interpreted as a signature of the ρ/ω * Present Address: Center for Nuclear Study, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan, email: ozawa@cns.s.u-tokyo.ac.jp † Present Address: ICEPP, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan ‡ Present Address: Physics Department, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan § Present Address: Fujitsu Corporation, 4-1-1, Kamikodanaka, Nakahara, Kawasaki, Kanagawa 211-8588, Japan * * Present Address: RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan † † Present Address: Xaxon Corporation,1-3-19, Tanimachi, Chu-ou, Osaka, Japan ‡ ‡ Present Address: Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 , Japan 1 modification at normal nuclear-matter density. 24.85.+p,25.30.-c Typeset using REVT E X 2 Recently, chiral property of QCD in hot(T = 0) or dense(ρ = 0) matter attracts wide interests in the field of hadron physics. The dynamical breaking of chiral symmetry in the QCD vacuum induces an effective mass of quarks, known as constituent quark mass. In hot and/or dense matter this broken symmetry is subject to restore partially or completely, and hence the properties of hadrons can be modified. To observe such an effect, measurements of in-medium decay of vector mesons, especially in the lepton-pair channel, are highly desirable to obtain directly the meson properties in matter [1].Although many heavy-ion experiments were carried out in CERN-SPS and BNL-AGS to study hot and dense matter, there was only an experiment which could address the mass modification of vector mesons. The CERES/NA45 collaboration measured low-mass electron pair productions in Pb-Au collisions at 158 A GeV [2], and observed an enhancement of e + e − pair yield in the mass range 0.3 < m ee < 0.7 GeV/c 2 over the expected yield from the known hadronic sources in pp collisions. This striking effect could be understood as a consequence of the mass modification of the ρ and ω meson in hot matter.In QCD the mass of vector mesons, mainly determined by the effective mass of quarks, is closely related toqq condensates ( qq ) which is an order parameter of the chiral symmetry of the QCD vacuum. In this framework a significant decrease of qq is expected not only at high temperature but also at normal nuclear density [3]. Using the QCD sum rule, Hatsuda and Lee theoretically predicted in-medium modification of the vector mesons [4]. According to this model, mass decrease at normal nuclear density is 120 ∼ 180 MeV/c 2 for the ω and ρ mesons and 20 ∼ 40 MeV/c 2 for the φ meson. Thus the measurements of such mesons, which are produced and decayed in a nucleus, are of great interest. The present experiment is one of the several experimental efforts [1...

The invariant mass spectra of e+e- pairs produced in 12 GeV proton-induced nuclear reactions are measured at the KEK Proton Synchrotron. On the low-mass side of the meson peak, a significant enhancement over the known hadronic sources has been observed. The mass spectra, including the excess, are well reproduced by a model that takes into account the density dependence of the vector meson mass modification, as theoretically predicted.

Below the freezing point of silver, radiation thermometers are generally calibrated by implementing the multi-point interpolation method using blackbody measurements at three or more calibration points, rather than the ITS-90 extrapolation technique. The interpolation method eliminates the need to measure the spectral responsivity and provides greater accuracy at the longer wavelengths required below the silver point. This article identifies all the sources of uncertainty associated with the interpolation method, in particular, those related to the reference blackbody temperatures (either variable-temperature or fixed-point blackbodies) and to the measured thermometer signals at these points. Estimates are given of the 'normal' and 'best' uncertainties currently achievable. A model of the thermometer response is used to propagate all the uncertainties at the reference points and provide a total uncertainty at any temperature within the calibration range. The multi-point method has the effect of constraining the total uncertainty over this range, unlike the ITS-90 technique for which the uncertainties propagate as T 2 . This article is a joint effort of the working group on radiation thermometry of the Consultative Committee for Thermometry (CCT), summarizing the knowledge and experience of all experts in this field.

Invariant mass spectra of e(+) e(-) pairs have been measured in 12 GeV p + A reactions to detect possible in-medium modification of vector mesons. Copper and carbon targets are used to study the nuclear-size dependence of e(+) e(-) invariant mass distributions. A significant excess on the low-mass side of the phi meson peak is observed in the low betagamma(= beta/square root(1-beta(2))) region of phi mesons (betagamma < 1.25) with copper targets. However, in the high betagamma region (betagamma > 1.25), spectral shapes of phi mesons are well described by the Breit-Wigner shape when experimental effects are considered. Thus, in addition to our earlier publications on rho/omega modification, this study has experimentally verified vector meson mass modification at normal nuclear density.

Melting and freezing plateaus were radiometrically observed for the metal-carbon eutectics Ni-C, Pd-C, Pt-C, and Ru-C, using graphite crucibles and black-body cavities. The graphite crucibles were able to withstand heat cycles without breaking. Since the crucible material is a component of the eutectic fixed-point material, the latter is inherently free of contamination from the crucible. The temperature differences between the melting and freezing plateaus were generally less than 0.1 C. The method seems to be a promising way of realizing a series of practical reference points above the copper point.