M. Naruki

Experimental signature of medium modifications for rho and omega mesons in the 12 GeV p+A reactions.

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.

Evidence for in-medium modification of the phi meson at normal nuclear density.

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.

Observation of rho/omega meson modification in nuclear matter.

We measured the invariant mass spectra of electron-positron pairs in the target rapidity region of 12-GeV p+A reactions. We have observed a significant difference in the mass spectra below the omega meson between p+C and p+Cu interactions. This difference indicates that the spectral shape of mesons is modified at normal nuclear-matter density.

Observation of the “K− pp”-like structure in the d(π+, K+) reaction at 1.69 GeV/c

We have observed a “

Mass production of hydrophobic silica aerogel and readout optics of Cherenkov light

K^{-}pp

Search for the Θ+ pentaquark via the π(-)p→K(-)X reaction at 1.92 GeV/c.

”-like structure in the

Inclusive spectrum of the d(π+, K+) reaction at 1.69 GeV/c

d(\pi ^{+ },K^{+ })

Nuclear-matter modification of decay widths in the phi-->e+e- and phi-->K+K- channels.

reaction at 1.69 GeV

Experimental signature of in-medium mass modification of vector mesons at normal nuclear density

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Nuclear mass number dependence of inclusive production of {omega} and {phi} mesons in 12 GeV p+A collisions

. In this reaction, a