ITEP 86-77 INSTITUTE OF THEORETICAL AND EXPERIMENTAL PHYSICS A.E.Asratyan, A.V.Fedotov, RA.Gorifchev, S.P. Krufchinin, M.A.Kubantsev, I.V.Makhlueva, V.I.Shekelyan, V.G.Shevchenko, V.V.Ammosov*} V.S.Burtovoy*} A.G.Denisov**, G.S.Gapienkox' x x V.A.Gapienko ) V.I.Klyukhin*'. V.I.Koreshev ^t x x x P.V.Pitukhin ), V.I.Sirotenko ^, E.A.SIobodyuk ^f V.G.Zae«zx) OBSERVATION OF THE CHARMED STRANGE PSEUDOVECTOR MESON CASCADE RADIATIVE DECAY Preprint Moscow -ATOMINFORM-1986 Institute for High Energy Phisics, Serpukhov, USSR У.'.л 533.I7.J M-I6 0В5ВПТАТЮИ О? ТЯВ СНАИШ) ЗТ1АН0В РЗВОЮГВСФОЖ ПЗОЯ CA3CADB RADlAfTO DKATt Preprint ГТВ? 86-77/ A.S.Aar»tyan, A.T.FtdotOT, F.A.OoritchOT *t al.t I АПЖтУОШ, 1Э86 - 8p. Abstract The antlneutrloo production and eaaeada radiatir* deoaj of the chanted strange paavdovaotor neaon are oba#rr«d. The paeudovaetor and raetor P aeaon тлвввш are aaaeured to b» (2547^60) Мет and (2123*15) Пат, raapeetiraly. - 2, raf. - 5 (6) Центральны» иауио-исстодомтвльскМ шнстшуг «нформмм я техмпю- акономическнх исслвоовмм* по атомной науке • технике (ЦНИИатомнмформ#,1966 The weak transitions wi -> P^i, Pgi with subsequent off- nueleon scattering of the vector (Py) or pseudovector (Fj[) charmed strange meson might account for the bulk of the F(el) neutrinoprbduction £i-2j. The experimental observation of the TOD-produeed P*" radiative decays P^~ -> ^P~ was indeed recen- ly reported by our group £3] (almost simultaneously with the •*•" results J4J). Reported in the present paper is the search for the radiative decays of the pseudorector (cs) mesons produ- ced in v H interactions. Analysed are the antineutrino data collected with the Fer- mi lab 15-ft bubble chamber filled with the heavy neon-hydrogen mix (the data as well as the charged current sample are descri- bed at some length In JVJ). The metho' employed is the reconstruction of the ground- state F~(1970) meson by its hadronic decay products and analysis of the gamma momentum spectrum in the f rest frame. The "recon- structed" T~ should be understood here as the collection of par- ticles with the invariant mass close to that of the 7(1970)t the par tides coming from the primary interaction vertex (the 7 is too short-lived to be observed as a track in the bubble chamber). Towards the P reconstruction, we try the following hadro- nio decay nodes : Г" -> У -#. KpT, Kp'rt0, ЪрГ-п*тГ, K§K*tr-ir~ 2 To clarify the procedure, a few remarks are necessary : i the pion and kaon masse* are arbitrarily ascribed to the charged track* (not identified as protons or electrons) ; ii to isolate the <P -> X*t~ decays, we select the X*K~palrs with mass in the interral 1020 - 15 Мет ( ~ 2 calculated standard deviations) ; iii in the case of У -• ^P X, 4? -* КИС? we reconstruct the *?> four-momentum, simply multiplying that of Kg by a factor mC?)/m(K|) (the к£ is not registered in the chamber). This approximate method is justified by the smallness of the 4» -> K^K° phase space. The induced "kinematic" uncertainty of the ? mass reconstruction is calculated to be—95t 75, and 50 Мет for the decay channels ?"-* *?*!'» ЯРтГп0, and , respeetirely ; IT to reconstruct the neutral pions, we select gamma pairs with шааь in the interval 135-20 Мет (in accordance with the width of the «° peak on the overall m~y швав plot}. The gas- mas that remain are called "odd". The decay sy&tem mass m is required to lie within one calculated standard deviation 4 of the ?(1970) mass: Дв < 4. The ralue of 6 is calculated individually for each systea by varying the momenta and angles of all the particles within the measure- ment errors (the kinematic uncertainty associated with 9 -& is also included). The typical o* value is ~100 ler for *PI, 9 -+ KgKj and *-50 Мет for the rest of the listed decay channels. 3 In the rec one true ted F~ meson rest frame we p3ot the mo- menta Ei of the odd (surviving the T5° rejection procedure) gam- mas employing two additional selection criteria. The first (on the eTent level) ie the constraint on the square of the four- momentum transferred from leptons to hadrons: Q < 2 Gev . The motivation ie that the VXD mechanism effectively cuts Q at the level of the order of (pseudo)vector meson mass squared. The second selection oriterium (on the combination level; is the cut * > .7 on the fractional visible hadronlc energy carried by th€ ?£f system. The latter is oriented towards the P»K -> T*H transitions with snail inelasticity. Plotted in Pig. la are the odd gamma momenta in the recon- structed P~ frame. Apart fro» en enhancement near 150 Mev sig- nalling the Щ~ -> У?* decay £3-*J, a cluster is observed at 400-600 Mev. To estiaate the background, w» plot s i a similar distribution» but with the shifted mass value, 1. e. 1.5*: Дш/о'^г.5 (••• M.g. 1b) ; 11 a similar distribution, but with the system charge sign inverted t *Pn+, «to. (ее* Pig. 1e). Comparison with the background wouldn't lead to any reliable positive Interpretation of the 400-600 Mev cluster In Pig. 1a. The two-dimensional plot in the (El» , Sin) plan* (by con- vention, BL. > E&9 ) for events with two odd gammas contribtt- ting to the one-dimensional distribution in Pig. la proves more Informative. In ths area 400* El, < 600 Mev, 100<iE» < 200 Xev an isolated group is observed which consists of 5 "cascade* 4 erenta. The risible width of the signal in both variables la consistent with the experimental resolution (the ganaa momentum measurement error is •~2O56). Of the two-dimensional background plots corresponding to the one-dimensional distributions of Pig. 1b and Tig. 1c, the former consists of a single point (EL, » 123 Мет, Ei2 - 67 Mev), while the latter is completely empty. We conclude that the back- ground in the area- 400-C S1^ < 600 Мет, 100<Etg < 200 Мет is small. Some characteristics of the five "cascade" events are lis- ted below (all quantities in Mev, the denotations ^_ and <&oo stand for T -^X^K" and <F — K|K° , respectively): Decay m- $ 3lv> ^jTiP 1994-40 ~?96 447 2157 2549 ^jTi^rT 1946-26 193 486 2154 2630 <5^тг~-п+тт" 1961^17 131 427 2097 2489 «S^ITVH" 1925-125 165 580 2129 2632 КрГп*тГ 1958^24 111 418 2078 2436 The moat likely interpretation of these events is the cas- cade radiative decay PJ" -* ^*у~» Pf" -* fe*" of *he Peewio" vector (cs) meson VHS-produeed in ТдЯ interactions; They allow for a simultaneous measurement of both the vector and pseudorec- 'Had It been an orbitally-excited rector (oa) state (and not the pseudovector one)» ita radiative decays would be grossly orershadowed by the strong t-war» IX channel (for шааааа отег - 2360 Mev). 5 tor BUMI t л(Ц) • (2547 * 64» Мет , ш(Ц) • (2123 * 15) Мет • * The reported я(?$) ralue agree* well with our previous measure- ment of 2106&18 Мет [у\, лш well •• the 1RGU3 and the T?C •*•" With m(PJJ) > 2500 Мет, one Bight expect the TJ radlatlTe decays to Ъе OTerwheleed by the strong a-ware D*X ohaaael. There- fore, our data taken aa a «hole indicate that the lowest pseudo- vector (ce) state lies just below the 0«K threshold (^2500 Мет). We thank the physicists from ГезжИаЪ and the Unlrereity of Miohigan for their contribution to the Initial stage of the experiment. Helpful discussions with M* A» Shifnan are grateful- ly acknowledged. &. >w Mg.1 Th* odd gum e«nt«r>-of-ataa «onwntrm epeott» for т *) «yetm* of rl^it elgB with ^•/6/<1.j Ъ) ariratmw of right sign with 1.5 < .Да/о* ^ 2.5 j o) ejatvmm of wrong eiga with Дш/& < 1. ?i«.2 The two-dimensional SJ, - B^ plot for «rente with two gammas contributing to the one-dieeneional tion in Pig. 1a. 8 EBFBHEBCBS 1. A r Ъ u с о г В.A. «t al. - SOT.Journ.Hucl.Phy».,1975,?1#13?t A r b tt s о т B.A. at al. - Soy.Journ.Bucl.Phye.,1975,22,173. 2. Chen M.S. «t al. - Жис1.Нцгво, 1977» B118, 345. 3. Aaratyan A.B. at al. Ж., Preprint ITBP, 1984, Я 99. leratyan А.1. et al. - Xbjra.Lett., 1985, 156B, 441. 4. A 1 Ь а г а В. «t al. - rhj-e.l»T.Lett., 1984, 53, 2465. libriebt •. at al. Pfaya.Latt., 1984, 146B, 25. 5. AmaeaoT T.T. at al. - *icl.Phya., 1981, B177» 365. А.Е.Асратян и др. Наблюдение каскадного радиационного распада псевдовокторного очарованного странного мезона. Работа постулата в ОЯГИ 16.04.86 Подписано к печати 16.04.86 TII7P8 :юр?лгт 60x90 I/I6 Офсета.печ. Усл.-печ.л.0,5. Уч.-изд.л.0,3. Тираж L'50 экз. Заказ 77 Индекс 3624 Цена 5 коп. Отпечатано в 1Ю2, 117259, Москва, БЛерецртщ<инс1сая,25 ИНДЕКС 3624 М..ПРЕПРИНТ ИТЭФ, 1086, N«77, с.1-8.