EMCal Run4 Recalibration Check Looking at K mass centroid and width Charles F. Maguire Vanderbilt University

Procedure for Mass Checking Using Stripe 2 CNTs as input processed with recalibrator Files divided into four groups (only valid runs considered) First half of ++ runs Second half of ++ runs First half of -- runs Second half of -- runs Analyze the East and West Arms separately East Arm has about half the yield of the West Arm Checks done for hot and dead towers, dual hit towers, DC ghosts Use 3 track matching with nominal 0.0 centroid (needs iteration) Mass spectrum fitting (will also compare with May PWG results) Mass-squared spectrum is fitted from 0.1 to 0.4 [GeV/c2]2 Fit function is 3 parameter background + Gaussian for the Kaon Background function is c1 + c2/chan2 + c3/chan4 {corrected version} Plan to investigate alternative background function for systematic check Use fourteen momentum bins from 0.325 to 0.975 GeV Lowest momentum bin has barely visible mass K+ peak October 17, 2005 EMCal Recalibration Check

Mass Centroid Dependence: sample fits K+ K+ K+ K+ 0.325 0.525 K K K K K+ K+ K+ K+ 0.975 0.825 K K K K October 17, 2005 EMCal Recalibration Check

Mass Centroid Dependence:++ Field Runs West Arm East Arm Clear charge sign dependence Some East-West dependence October 17, 2005 EMCal Recalibration Check

Mass Centroid Dependence:-- Field Runs West Arm East Arm Clear charge sign dependence More East-West dependence October 17, 2005 EMCal Recalibration Check

Mass Centroid Dependence: ++ to -- transition West Arm East Arm No large transition effect October 17, 2005 EMCal Recalibration Check

Mass Centroid Dependence: compare to PWG West Arm East Arm May 10 PWG result similar October 17, 2005 EMCal Recalibration Check

Mass Width Dependence: ++ Field West Arm East Arm Distinct charge dependence October 17, 2005 EMCal Recalibration Check

Mass Width Dependence: -- Field West Arm East Arm Distinct charge dependence October 17, 2005 EMCal Recalibration Check

Mass Width Dependence: ++ to -- transition West Arm East Arm October 17, 2005 EMCal Recalibration Check

Mass Width Dependence: compare to PWG West Arm East Arm PWG  are lower Need to check fitting function dependence October 17, 2005 EMCal Recalibration Check

EMCal Recalibration Check Summary Kaon Mass Centroid Clear difference between K+ and K- at lower half of momentum range Difference is almost the same whether in the ++ or the -- field Implies this is not a detector or software artifact due to trajectory bend Is there any physics explanation for the K+ and K- difference? Should look at the proton and the anti-proton masses Momentum dependence similar to that observed in May 10 PWG presentation by Dipali and Debsankar There is some East-West dependence, especially in -- field runs Kaon Mass Width Linear rise of width for momentum greater than 0.5 GeV/c Widths below 0.5 GeV/c are approximately constant or rising The K+ widths at the lowest momenta are a little larger than the K- widths The widths derived in this study are systematically larger than the widths shown in the PWG presentation: need to check functional dependencies October 17, 2005 EMCal Recalibration Check