Hycal Energy Resolution, Timing, &Trigger Efficiency,

A cumulative study.

Chris Mauney

Hycal Energy Resolution - Purpose

• In order to achieve proper estimation of systematic errors, as well as producing the most accurate simulation models, the energy resolution of the calorimeter were determined for each module.

Hycal Energy Resolution – Data Collection

• Data was acquired during “snake scans,” dry-runs for the purpose of calibrating and testing calorimeter.

• The calorimeter is constituted by two types of detectors, lead glass and lead tungstate (PbWO4).

• The snake scans were done with an incident photon beam of energies between 1 GeV and 5.5 GeV, which were categorized into “energy bins” between 1 and 15.

Hycal Energy Resolution – Data Analysis

• Histograms were made for the ratio of energy defined by Hycal and by Tagger (which has ~0.1% energy resolution).

• After all histograms had been properly fit with a Gaussian, parameters of the fits were extracted, i.e. amplitude, mean, and sigma (along w/ errors).

•These parameters were separately gathered, and graphed for each channel, as a function of energy.

Hycal Energy Resolution – Data Analysis

• These graphed parameters were fit with the function:

• A represents constant term of energy resolution, B represents energy fluctuations (“stochastic” term), and C represents electronic noise.

• E represents beam energy

E

C

E

BA

Hycal Energy Resolution – Data Analysis

• Parameter C was fixed, parameters A and B were extracted and graphed.

• Channels with ID less than 1000 were lead glass, and channels with ID 1000 and up were tungstate. These channels were separated for a more precise result.

Hycal Energy Resolution – Data Analysis

• Parameter B was altered by roc-4 modules, which experienced higher than average distortion.

• Shown Below is a diagram of roc-4 in Hycal.

Hycal Energy Resolution – Final Analysis

• Hycal Resolution was extracted by looking at all sigma values for one energy bin.

• Shown right are the results from the two snake scans, both using energy bin 14 (~5GeV).

• Resolution seems to hover around 1.65-1.8% (for crystal channels).

Timing - Purpose

• To more properly understand Hycal timing in triggers.

• This data will be used in timing alignment and simulation processing.

Timing – Data Processing

• Along with resolution information, timing data was also extracted.

• Thankfully, there were many fewer histograms dealing with timing. This allowed for faster processing.

Timing – Data Analysis• Much like

resolution analysis, these histograms were fitted with a Gaussian, and had fit parameters stored for further analysis.

• Time Difference refers to the time between a beam trigger and a Hycal trigger

Timing – Data Analysis• A problem was

encountered with the first snake scan. The top graph shown right has duel peaks – indicating two signals. This issue only arose for lead glass channels.

• The lower graph is from the same channel in the second snake scan. Clearly this issue was not present during that run

• The error was attributed to a broken or loose cable in the detector, causing a kind of internal reflection. These results were excluded in the final analysis.

Timing – Final Analysis• Fit parameters were

gathered into one histogram, both for collective mean and sigma.

• Shown right top are mean values for first snake, and right bottom are mean values from second snake

Trigger Efficiency - Purpose

• Before this study, a detailed examination of trigger efficiency was lacking. This information will be used to see how close efficiency is to 100%. This will be used in π0 lifetime error budget.

• This is the first study done on trigger efficiency, more important data analysis needing to be done beforehand.

Trigger Efficiency – Data Processing

• Along with resolution and timing, efficiency data was extracted from snake scan data.

• However, for efficiency, analysis was only done one the first snake scan.

• First, data were selected with a proper beam trigger and energy deposition in Hycal. Then event count in sample were checked, followed by checking if sample had a Hycal trigger (trigger bit2).

Trigger Efficiency – Data Analysis

• To say it more accurately, what as analyzed was trigger miss efficiency, i.e. trigger miss rate.

Trigger Efficiency – Data Analysis

• Channels in the highlighted box shown (bottom right) were disconnected during the scan, and yielded nearly 0% efficiency.

• Since then, this hardware problem has been corrected.

Trigger Efficiency – Final Analysis• It was discovered that

nearly all channels, in energy bins greater than 10 (>2.8 GeV) , had 100% efficiency.

• Some channels were broken: 12, 732, 900.

• Other channels had bad efficiency due to a dead dinode: 79, 268, 877, and 1849.

• Shown right is a histogram, in logarithmic scale, of all channels (excluding the disconnected block and problem channels mentioned above).

Special Thanks

• Dr. Liping Gan

• Ilia Larin

• Dr. Ashot Gasparian

• Aram Teymurazyan

• Dr. Pawel Ambrozewicz