Cazzoli, E.G.

Cnops, A.M.

Connolly, P.L.

Louttit, R.I.

Murtagh, M.J.

Palmer, R.B.

Samios, N.P.

Tso, T.T.

Williams, H.H.

Cazzoli, E. G.

Cnops, A. M.

Connolly, P. L.

Louttit, R. I.

Murtagh, M. J.

Palmer, R. B.

Samios, N. P.

Tso, T. T.

Williams, H. H.

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Presented at:International Colloquium onNeutrino Physics at High EnergyMarch 18-20, 1975Paris, FranceBNL 20013HG-309MEASUREMENT OF THE RATIO OF NEUTRINOTOTAL CROSS SECTIONS ON HYDROGEN AND DEUTERIUMIN THE BROOKHAVEN 7-ft. BUBBLE CHAMBER*E.G. Cazzoli, A.M. Cnops , P.L. Connolly, R.I. Louttit,M.J. Murtagh, R.B. Palmer, N.P. Samios, T.T. Tso, andH.H. Williams++Brookhaven National LaboratoryUpton, New York 11973We present charged current neutrino interactions obtained in hy-drogen and deuterium as a function of charged track multiplicity. Theratio of neutrino fluxes in the two exposures is obtained from the twosamples of the reaction vp •*• u pit . The ratio of total charged cur-rent cross sections on hydrogen and deuterium is thus obtained andpresented as a function of neutrino energy. The result obtained forneutrino energies above 2 GeV is:0.40 + 0.10msmNOTICEThis report was prepared as an account of worksponsored by the United States Government. Neithertrie United States nor the United States EnergyResearch and Development Administration, nor any oftheir employees, nor any of their contractors,subcontractors, or theit employees, makes anywarranty, express or implied, ot assumes any legalliability oi responsibility for the accuracy, completenessOT usefulness of any information, apparatus, product orprocess disclosed, or repiesents that its use would notinfringe privately owned rights.* Work performed under the auspices of the Energy Research & De-velopment Administration.t Currently on leave of absence.it Present address: University of Pennsylvania, Philadelphia, Pa.19174.DISTRIBUTES OF THIS DOCUMENT UNLIMITED1.INTRODUCTIONThe data sample and the initial event selection procedure for thestudy of charge current interactions in hydrogen and deuterium wereidentical to those discussed previously with regards to the neutral cur-rent study . The visible momentum vector for each event was calculatedand events withP . > 400 MeV/cvis —< 35°<35°were accepted as beam associated events. Charged current candidateswere then defined as events which satisfied the above cuts and had apossible u~ track. A total of 93 events in hydrogen and 211 events indeuterium were obtained from 62K pictures in hydrogen and 68K in deu-terium. The actual breakdown of the events into, the number of visibleprongs is shown in Table I.To calculate the hydrogen and deuterium cross section ratio, itis necessary to establish the relative flux normalization of the twosets of data. This was done by measuring the number of uniquevp -*• y~pirevents in each case. The procedure for selecting these events in both,iliquids is discussed. Then the method for calculating the neutrinoenergy is outlined and the cross section ratio as a function of energy \calculated. °SELECTION OF u~pu+ EVENTS jy • - .In hydrogen the selection of unique ;; , •;vp •> V PT ' lif?'''::'-t."v '•••was made using the variable llnr^1 ';EMPX = (Ev - Mp) - Pvxwhere Ev, Pvx are the total visible energy and the component in thebeam direction of the visible momentum. If there are no neutrals mis-sing EMPX ̂  0 while for neutrals missing EMPX is driven negative. Fur-thermore, for events with no neutrals missing the visible momentumvector should point approximately in the beam direction. In hydrogenthan u~pir final states with no neutrals missing were defined to bev pn events for which/EM?X/ <. 30 MeV9vis * 6 ° 'where 6 . is the angle between the visible momentum vector and theneutrino beam direction (Fig. 1). A plot of the pff mass for the 59selected events shows a clear A signal (Fig. 2).A similar selection procedure was applied in deuterium. However,here the presence of a spectator particle causes a broadening of theEMPX distribution. From a study of the quasi-elastic events withouta visible spectatorvd •* u~p(pg)a width of 140 MeV for the EMPX distribution was determined. Uniquep~pn+ final states in deuterium were defined to be y'pn events forwhich (Fig. 3)/EMPX/ <. 140 MeV6 , < 8°visAgain 59 events satisfy these criteria and the pir mass distribution(Fig. 4) shows a clear A signal.CALCULATION OF THE NEUTRINO ENERGYA number of assumptions are required in the calculation of theneutrino energy for each event. The first set of assumptions cover3.t:ie spectators In the deuterium data. If the conditionsEMPX < 140, 6 . < 8°"̂" VXSwere satisfied for the event, then it was assumed that no spectator wasvisible. In this case the energy was calculated as in the hydrogenfilm. If a spectator was observed, then the correct deuterium energymomentum equations were used in calculating the neutrino energy.The second set of assumptions refer to the absence or presence ofneutral particles in the final state. As discussed previously, if inhydrogen/EMPX/ <_ 30 MeV, 6 ^ <. 6°or in deuterium/EMPX/ <_ 140 MeV, e y i s <, 8°then no neutral particles are assumed to be present in the final state.If these conditions are not satisfied, then it is assumed that onlyone neutral particle is missing. If a proton has been observed then aTT is assumed to be missing, but if no proton is present a neutron isassumed and the neutrino energy calculated accordingly in each case.HYDROGEN-DEUTERIUM CROSS SECTION RATIOSThe calculated cross section ratio for hydrogen and deuterium asa function of energy is shown in Fig. 5. At low energy (< 1.5 GeV)the total corss sections are composed almost entirely of the quasi- •I j •elastic and the A final states. The cross section ratio for these2channels is calculated from the measured cross sections and shown asthe solid curve in the figure. The predicted ratio from the quark V.3 :-;parton model is 0.39. If one considers data with neutrino energy ;:»v ••-,.above 2 GeV to be in the scaling region, then the measured cross sec- U ..•tion ratio in this region is found to be: i|;a(H_)- - 0.40 + 0.10 :References1. Study of Neutral Current Interactions in the 7-fc. Bubble Chamber,E. G. Cazzoli, et_ al_., reported at this conference.2. J. Cambell, et al., Phys. Rev. Letters, Vol. JJO, p. 335 (1973);W. A. Mann, et_al., Phys. Rev. Letters, Vol. J}1_, p. 844 (1973).3. A. de Rujula, e£ al., Rev. of Modern Phys., Vol. 4£, p. 391 (1974).TABLE ICHARGED CURRENT EVENT SAMPLE// Prongs23456789H287501(raw) D, (corrected*)651181312210095981692100^Spectator proton tracks not included in # prongs.30Gvis .Degrees2010•0••ai iHYDROGEN DATA*am•*• • # •T300.0 -200.0 -100.0EMP2 = (EVIS-»p)-(PVIS)x in MeVPlot of EMPX versus the Angle of the Visible Momentum Vector vithRespect to the Beam Direction.. 1HO10OtoA7>,-po* le.hP*\ ± loo.in nFig. 2ISOO 00 ISO'OBfiPX INFig. Jto51^ lO-O4-t-6 2-0!i .'Off"1'Fig. 4r;v\0 r03 -0-6 -0.2 •T_ p^rt sLEcr^oP^oacrio^<rC/fp) •*-| 1 1idBUBCTKOPfi O SUCTIONFig. 3

Measurement of the ratio of neutrino total cross sections on hydrogen and deuterium in the Brookhaven 7-ft. bubble chamber

Measurement of the ratio of neutrino total cross sections on hydrogen and deuterium in the Brookhaven 7-ft. bubble chamber

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