) of the Cell class is created containing information about events associated with the cell. Events are added to the Cell instance

Transcription

1 Calbraton Method Instances of the Cell class (one nstance for each FMS cell) contan ADC raw data and methods assocated wth each partcular FMS cell. The calbraton method ncludes event selecton (Class Cell Creaton) followed by teraton of reconstructon and recalbraton for each Cell. The steps are showed below. 1. Cell Class Creaton. For each small cell, an nstance ( Cell ) of the Cell class s created contanng nformaton about events assocated wth the cell. Events are added to the Cell nstance Cell only f the followng are satsfed. The event has 2 photons where the hgher energy photon lands n the cell n queston. A photon s counted only f photon energy > 4 GeV. Events are ncluded n the nstance f there are 2 and only 2 photons n an angular cone of.45 Radans. 2. Iterate for calbraton constants (lke those found n Fpdcorr.txt) events n each Cell class nstance are re-reconstructed based upon current calbraton constants. The result of teraton s that the calbraton constants can change. The steps n an teraton cycle are: Reconstruct events n a partcular cell nstance. Make mass vs energy dstrbuton for events wth par energy > 1 GeV and wth the hgh energy photon n the cell n queston. Make an energy dstrbuton for photon pars that have mass between.1 GeV and.3 GeV. Ft the mass vs energy dstrbuton to a lnear functon M(E). Evaluate M(45 GeV). For each cell, we count the number of events per GeV at energy of 65 GeV. Ft the hgh energy part of the energy dstrbuton to a form N( E) N e E65GeV.2GeV, where N s the number of events n 1 GeV energy bns. For each Cell, the constant N ( N) s determned n a ft to the energy dstrbuton n the th cell. Compare events per 65 GeV to model. As a model for the rapdty and energy dependence, we wll start wth the form: n( E, Y) n p4( Y) e e ( Y 3.65) ( E65 GeV ) (For ths data set, we choose n =3.) and where p4(y) s a 4 th order polynomal n Y, Intally we wll assume p4(y)=1 but the polynomal wll change on each round of teraton. The rato of measured count to modeled count s

2 r N(65 GeV ) n(65 GeV, Y ). For each cell, two factors are determned. The frst s.135 Factor1 M (45 GeV ) For each cell, the second factor s determned by the rato of r to 1. We defne the second factor, n Factor2 65 GeV, Y r n(65 GeV, Y ) r e Factor GeV 5GeV Factor2 5GeV Log r 5GeV Log r 65 1 Factor Log r 65GeV ( Factor 1 Factor 2) The gan correcton for ths cell wll be changed gcorr 1 gcorr Update p4(y) to fx average masses vs. rapdty. After the gans of each cell has been ndependently modfed as mentoned above n step 2), the polynomally p4(y) s adjusted. A plot of Factor 1 vs. pseudo-rapdty for all cells s ftted to a polynomal and the resultng functon multples the old p4(y) to get a new p4(y). Fnally, we return to tem 2 and terate. In short, the model dstrbuton as a functon of pseudo-rapdty s modfed for the next round of teraton so that the masses tend toward the pon mass at each regon of pseudo-rapdty. 4. Ths means that the changes n gan wll be weghted 5% toward brngng the average mass n each regon of pseudo-rapdty to the pon mass and 5% toward brngng the event GeV toward the nomnal rapdty shape. Ths s bascally tendng to make the event GeV smooth as a functon of rapdty but does not presuppose the shape of that rapdty dependence of the cross secton. We do the teratons ether on a set of Cell nstances. Reconstructon of the all the SMALL

3 Cell FMS nstances takes several hours on one of our PC s runnng lnux. It can also be submtted va condor, one job per cell where teraton can take a small fracton of an hour per pass. Small Cell Results The dea of the prevous procedure s to calbrate wth the constrant that 1. the two photons mass should reconstruct to the nomnal 2. that the cross secton for mass and producton should be ndependent of azmuth. The basc assumpton s that at hgh energy, the number of $\p^$ events that depost the hgher energy photon n a partcular cell and wth $\p^$ energy between 65 and 66 GeV should be relatvely unaffected by trgger threshold or geometrcal acceptance. Clearly the assumptons are only approxmately true. The gan teraton hstory for each small FMS cell s found here. Ths fle contans a hstory graph (gancorr vs teraton number) for every cell startng wth the lower left cell n Fgure 1 (referred to as Row c_d2) meanng row=, col=, North. The resultng energy and mass dstrbutons are shown here. There s one page per cell. In red s a the energy and mass dstrbuton for the cell n queston. On the rght, we see the energy and mass dstrbutons for smulated data (smulaton trgger not yet correct). Fgures smlar to Fgure 1, Fgure 2 and Fgure 3 for Monte Carlo smulatons are shown here. More must be done on smulaton result.

4 Fgure 1: The color ndcates the number of events per energy GeV for all small cells.

5 Fgure 2: The same data shown n Fgure 1 (one pont per cell) but plotted as a functon of cell rapdty. S

6 Fgure 3: Raton of.135 to pon mass for each small FMS cell.