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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2010, vol. 105, p. -

Search for a low mass particle decaying into μ+μ - in B0→K*0X and B0→ρ0X at Belle

Hyun H. J., Park H. K., Kim H. O., Park H., Aihara H., Arinstein K., Aushev T., Bakich A. M., Barberio E., Bay A., Belous K., Bischofberger M., Bondar A., Bozek A., Bračko M., Chang M. C., Chang P., Chao Y., Chen A., Chen P., Cheon B. G., Cho I. S., Choi Y., Dalseno J., Danilov M., Dash M., Drutskoy A., Eidelman S., Gabyshev N., Golob B., Ha H., Hara T., Horii Y., Hoshi Y., Hou W. S., Hsiung Y. B., Inami K., Iwasaki Y., Joshi N. J., Kah D. H., Kang J. H., Kapusta P., Kawasaki T., Kichimi H., Kiesling C., Kim H. J., Kim J. H., Kim M. J., Ko B. R., Kodyš P., Križan P., Kuzmin A., Kwon Y. J., Kyeong S. H., Lange J. S., Lee S. H., Li J., Liventsev D., Louvot R., Matyja A., McOnie S., Miyabayashi K., Miyata H., Miyazaki Y., Mohanty G. B., Nakano E., Nakazawa H., Nishida S., Nishimura K., Nitoh O., Ohshima T., Okuno S., Olsen S. L., Palka H., Park C. W., Pestotnik R., Petrič M., Piilonen L. E., Ryu S., Sahoo H., Sakai Y., Schneider O., Sevior M. E., Shapkin M., Shiu J. G., Shwartz B., Singh J. B., Stanič S.

We search for dimuon decays of a low mass particle in the decays B0→K*0X and B0→ρ0X using a data sample of 657×106BB̄ events collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We find no evidence for such a particle in the mass range from 212MeV/c2 to 300MeV/c2 for lifetimes below 10-12s, and set upper limits on its branching fractions. In particular, we search for a particle with a mass of 214.3MeV/c2 reported by the HyperCP experiment, and obtain upper limits on the products B(B0→K *0X)×B(X→μ+μ-)<2. 26(2.27)×10-8 and B(B0→ρ0X) ×B(X→μ+μ-)<1.73(1.73)×10 -8 at 90% C.L. for a scalar (vector) X particle. © 2010 The American Physical Society.