Daniel J. Cruz Dept. of Physics and Astronomy Texas A&M University

Presentation  Overview  Utilizing Cuts  Actual Experiment  Results  Summary 2

Overview  Utilize cuts in physics to better analyze data  Show that care needs to be taken when making cuts (cannot make them blindly)  Sometimes two cuts AREN’T better than one cut 3

Utilizing Cuts 4

One Cut Analysis  Cut away part of data  Stick with most useful  Free to move cut selection (in this case, 200 GeV) 5

Two Cut Analysis  Cut away part of data, then separate rest in two cuts  Cut A is original cut, cut B is new cut within original  Makes data more manageable  Can move both cuts, or keep one cut (A) static while moving other cut (B) 6

Actual Experiment 7

Expected Cross Sections  We look for 95% confidence limit on expected cross section, σ production  Utilize cuts technique to optimize σ 95  Used modified Fortran Limiting Calculator program, coded by Dr. Joel Walker of Sam Houston State University 8

Experiment  Data taken from Eunsin Lee’s Ph.D. thesis at Texas A&M, Phys. Rev. Lett. 104, (2010) Phys. Rev. Lett. 104, (2010)  Binned values were used, as well as fitted values  Graph provided by Chris Davis (modified graph in slides 5 and 6) 9

Background  Fitted background  Used an exponential curve  Red dots are fit, black dots are actual data 10

Acceptance  Fitted acceptance  Used a Gaussian curve  Red dots are fit, black dots are actual data 11

One Cut Experiment  Red dots are actual data  Black dots are fitted data  Optimum is 22 fb at 240 GeV (22.5 fb at 250 GeV for fitted curve)  What about two cuts? 12

Two Cut Experiment  Minimum of 21 fb at (240,36)  However, places where σ 95 > 22 fb  Better than one cut in places, worse in other places!  Graph provided by Chris Davis 13

Results 14

How much better can you get?  Plot of cut A (250 GeV) as a function of cut B; black dotted line indicates limit at 250 GeV (22.45 fb)  By manipulating our cut B, we can optimize to 21.3 fb (achieved with cut B at 350 GeV) 15

One Cut -> Two Cut  You always (ok, most of the time) get an improvement  Have to be careful in order to maximize improvement  Shown is 2-D Minimum Limit vs. Cut A (notice that lowest limit achieved is better than 1-D) 16

Summary  In MOST cases, two cuts > one cut (have to be careful, though)  Delicate in how to choose cut B (otherwise, you get result which is roughly equal to one cut) 17