Measurement of fragmentation properties of charmed particle CHORUS Workshop June 2004, Rome A.Kayış Topaksu

Fragmentation variables definitions Z → fraction of the total hadronic jet energy carried by the meson z=E/ν, z=E/(ν+M) where E is the energy of the meson, ν is the energy transferred to the hadronic system and M is the nucleon mass. X Feynman→ is longitudinal variables defined as x F =2P ║ * /W in the c.m of hadronic system where P ║ * =γ(P ║ -βE), P ║ is the longitudinal momentum of meson wrt the direction of the hadronic system p t → transverse momentum of the meson wrt the direction of hadronic sys.

NOMAD 35 D *+ events = 0.67±0.02 ε p =0.075±0.028 =0.47±0.05 = 0.23±0.06 B=3.38±0.40 E events (57 D 0, 41 D +, 6 D s +, 15 Л c + ) ε p =0.076±0.014 from A=0.620±0.092 B=3.25±0.37 Some results measured by other experiments CDHS = 0.68±0.05 ε p =[0.02, 0.14] CCFR = 0.56±0.03 ε p =0.22±0.05 CHARM II = 0.66±0.03 ε p =0.072±0.017 BEBC = 0.59±0.03 ±0.08

Correlation between average geometrical angle of daughters and parent mom and unfolded mom dist. The measured distribution is little softer compared to MC

z-distribution Fitted function (Peterson) D p (z)=N/{z[1-(1/z)-ε p (1- z)] 2 } = 0.58±0.06±0.04 ε p =0.136 ±

X F distribution = 0.367±0.038±0.001 A= 0.876±0.152±0.02 Most charmed particles are produced in the forward region A is defined as forward-backward asymmetry

Θ out distribution It is defined as angle out of the plane formed by muon and neutrino Mean value 0.030±0.002

Efficiency and Background evaluation Standard charm data sample used (1,076 D 0 events) 1)There is no clear effiency dependence on the cuts applied 2)Total number of background events are 37 coming from K 0 and Λ 0 3)Some uncertainity introduced by the correction for the fragmentation model 4)Largest systematic error is the uncertainty of the energy meas. in the calo(~5%) 5)Resolution on the direction of D 0 is the order of 1-2 mrad

Summary and Outlook The measured value of ε tends to vary considerably between the experiment. Also some other differences in other parameters observed. It is not clear whether these differences are due to unknown systematics or other causes, ie, the charmed particle mixture are not the same for each experiment. For example, NOMAD used only D*s and E531 gave their result on all charged and neutral charmed particles. The first draft of paper has been written and sent to referee Still some study on systematics Waiting for comments....