Student Abstracts at Fermilab:

Analysis of the CDF II Data in Search of the Higgs Boson Decaying to Two Photons. CALLIE DEMAY (University of Illinois, Urbana-Champaign, IL, 61820) CRAIG GROUP (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

Although the Standard Model is unbelievably accurate, the one fundamental aspect needed to complete the model, a massive particle called the Higgs Boson, has not yet been discovered. In this investigation, we searched for a non-Standard Model, fermiophobic Higgs, which would decay to two photons. This decay mode is predicted to have a very small branching fraction according to the Standard Model; however, some models predict a higher branching fraction. We initially optimized selection criteria in order to become as sensitive as possible to the signal region. Using the 2fb^-1 of data provided by Fermilab’s Tevatron and collected by the Collider Detector at Fermilab (CDF) experiment, we were unable to see a signal for the Higgs; therefore, the focus of our research shifted to placing a limit on the cross section for the Higgs in the fermiophobic model. We were able to place a lower limit of 99 GeV on the mass of the fermiophobic Higgs. This limit is currently the best in the world for a hadron collider. The previous limits at Fermilab included one by CDF at 82 GeV, and one by DZero at about 90 GeV. However, the world’s best limit of 109.7 GeV was placed by the Large Electron-Positron Collider (LEP) in Switzerland. Although we were not able to find a Higgs signal, the techniques used to improve sensitivity to photon events will be useful in the next generation of collider experiments, which will be more sensitive to the small branching fraction of diphoton events.

Analysis of the Directivity of a Defective R-F (Radio- Frequency) Coupler Using a Network Analyzer. ZEPHRA BELL (Southern University and A & M College, Baton Rouge, LA, 70807) DR. TERRENCE REESE (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

The R-F couplers that we tested were used in a project called HINS at Fermi National Accelerator Laboratory ( Fermilab). HINS stands for High Intensity Neutrino Sources. These couplers are arranged in a transmission line at Fermilab. The couplers are crucial for the transfer of power in an R-F cavity. However, one of the couplers in the transmission line seemed to be defective. The high power signal down the "line" in the reflected power was too low from that in the forward port. It was measured to be only 13 dB when it should have been 60 dB. Therefore, initially, three different methods were used to test the defective coupler: 1) The connector cables attenuation was measured. Connector cables are used to attach the port of the coupler to other pieces of the R-F cavity. The cable attenuation and the reflection load were good. This meant that the coupler did not have power flowing through faulty cables. 2) Low power in the switch was generated. This still reflected a low signal of 13 dB. 3) Finally, the coupler was physically removed and tested directly. It still reflected a low signal of 13 dB. Hence, the coupler was brought to our team to see if we could determine the defects of the coupler through rigorous testing of the ports and internal modifications.

Comparison of Land Management Practices on Common Wood Nymph Butterfly Populations. TARA SCHWASS (Western Illinois University, Macomb, IL, 61455) ROD WALTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

Diversity of habitat and variety of wildlife has been increasing through restoration and land management techniques at Fermi National Accelerator Laboratory (Fermilab). These land management techniques are crucial to restoring and sustaining the natural habitats and native species of the area. This study examined the effects of land management techniques on the burned restored prairie, unburned restored prairie and mowed non-native grasslands and how these techniques affected local butterfly populations of Cercyonis pegala, the common wood nymph. Originally native to the prairie, the common wood nymph now occupies a wide range of habitat that includes not only prairie but also non-native grasslands, open woodlands, fields, marshes, savanna, and road sides. Transect counts were used to survey the abundance of wood nymphs for each of the five sites studied. A similar study performed last year included two of the same sites studied this year. Results were analyzed using a t-test, Mann-Whitney U-test, Spearman correlation, and Pearson correlation. Our results indicated the prairie had significantly more butterflies than the non-native grasslands and also weather variables did not significantly affect butterfly counts. Our results differed greatly from the study performed last year where non-native grasslands had more butterflies than the native prairie site. These varying results are likely due to the timing of the land management techniques at the sites. However, other possible explanations for the results may be vegetation differences in growth, abundance, and density, and/or butterfly behavior. A continuation of this study should include the same sites after a new season of burning and mowing to examine long-term effects of land management techniques and also to gain a better understanding of butterfly ecology at Fermilab.

Cosmic Ray Studies. MARGE BARDEEN (University of Illinois, Urbana, IL, 60137) MICHAEL BARDEEN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

I am writing this memorandum to suggest we segue into a slightly different direction for the QuarkNet evaluation. Based on last year’s Review, we are charged with collecting “metrics.” The issue, as I see it, is that the review recommendations are based on an unrealistic view of QuarkNet and that the current goals do not fit what the program has evolved into.

Effect of Pipes in a Tank to be Purged of Oxygen. LAURA ZANTOUT (University of Minnesota, Minneapolis, MN, 55455) STEPHEN PORDES (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

To produce a viable 50kton LArTPC (liquid argon time projection chamber), as proposed, the liquid argon within must reach a purity level of 10ppt oxygen. The purpose of the Daisy experiment is to determine if pipes used as structural components inside this detector would trap air and cause virtual leaks. A 2 cubic foot tank filled with 50 half-inch diameter pipes was used to simulate the structure that would be within the detector. As argon flowed through the tank, oxygen levels were monitored both on the gas outlet and within using monitors of various sensitivities. Several variations were run: with an internal fan, without a fan, and with one end of the pipes capped. Plots of percent oxygen vs. time for all of the runs were fit well by perfect mixing equations. This suggests that oxygen was not trapped in the pipes, but instead diffused out quickly. Other turbulence (such as convection currents) may have also accounted for some mixing, especially in the capped run. It appears that building a structure of much longer pipes will not contaminate the liquid argon inside a detector via virtual leaks, as long as mixing through diffusion is given time to progress, or sped up by a fan.

Flux Jumps in Nb3Sn Superconducting Accelerator Magnets and Implications for a Current Dependent Quench Protection System. CONOR DONNELLY and SAID RAHIMZADEH-KALALEH (Embry-Riddle Aeronautical University, Daytona Beach, FL, 32114) MICHAEL TARTAGLIA (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

With the upcoming inauguration of the Large Hadron Collider (LHC), the practical limit in the performance of Niobium Titanium (NbTi) superconductors will be reached based on the properties of the material. Fermi National Accelerator Laboratory has been developing a new generation of superconducting accelerator magnets based on Niobium Tin (Nb3Sn) intended for a luminosity upgrade to the LHC. The performance of these magnets has been found to be below the expected level due to thermomagnetic instabilities present in the superconductor. In order to develop better magnets for future machines, it is essential to fully understand these instabilities, which are characterized by fast voltage excursions or spikes. For this purpose, a new software application was developed to automate the analysis of voltage spikes in superconducting Nb3Sn magnets. Using the new software, the current dependence of spike amplitudes was determined, which demonstrated the possibility to use a current dependent quench protection threshold. Such a threshold could avoid premature system trips at low current due to non-quenching voltage spikes. This work presents quantitative and analytical studies on voltage spikes arising from flux jumps in superconducting Nb3Sn magnets as well as the features of the software developed for the analysis.

Plateauing Cosmic Ray Detectors to Achieve Optimum Operating Voltage. ELISSA KNOFF (Northwestern University, Evanston, IL, 60208) ROBERT PETERSON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

Through QuarkNet, students across the country have access to cosmic ray detectors in their high school classrooms. These detectors operate using scintillator and a photomultiplier tube (PMT). A data acquisition (DAQ) board counts cosmic ray hits from the counters. Through an online e-Lab, students can analyze and share their data. In order to collect viable data, the PMTs should operate at their plateau voltages. In these plateau ranges, the number of counts per minute remains relatively constant with small changes in PMT voltage. We sought to plateau the counters in the test array and to clarify the plateauing procedure itself. In order to most effectively plateau the counters, the counters should be stacked and programmed to record the number of coincident hits as well as their singles rates. We also changed the threshold value that a signal must exceed in order to record a hit and replateaued the counters. For counter 1, counter 2, and counter 3, we found plateau voltages around 1V. The singles rate plateau was very small, while the coincidence plateau was very long. The plateau voltages corresponded to a singles rate of 700-850 counts per minute. We found very little effect of changing the threshold voltages. Our chosen plateau voltages produced good performance studies on the e-Lab. Keeping in mind the nature of the experiments conducted by the high school students, we recommend a streamlined plateauing process. Because changing the threshold did not drastically affect the plateau voltage or the performance study, students should choose a threshold value, construct plateau graphs, and analyze their data using a performance study. Even if the counters operate slightly off their plateau voltage, they should deliver good performance studies and return reliable results.

The oak savanna. ASHLEY WENTLAND (University of Illinois at Chicago, Chicago, IL, 60047) ROD WALTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

The oak savanna, a mixture of prairie grasses, forbs and scattered tress, mainly oaks, was one of the major natural communities of the Midwest. Today, they are a top concern for restoration. Our objective was to document and characterize the tree population and age structure of the oak savanna by examining relative density, relative frequency, and relative cover for most common species. We conducted tree research in the remnant savanna on Fermi National Accelerator Laboratory’s property using the point-centered quarter method. We also prepared soil samples for analyses by First Environmental Laboratories, Inc. in Naperville, Illinois. Ca++ and Mg++ concentrations were identified for each soil sample. The north side of the savanna has a high tree and vegetation density compared to the south side where there is an abundance of open space and prairie grass. Bur Oak (Q. macrocarpa) is by far the most important species in the savanna. However, the basswood (T. Americana), white ash (F. Americana), and black cherry (P. serotina) are slowly dominating the oak savanna at Fermilab, which poses a problem. The data suggest that the north side of the savanna is degraded compared to the description of the healthier side of the savanna. The savanna is being invaded by trees and vegetation and may convert into a woodland if nothing is done. Some possible strategies indicated by our results that may help aid restoration are: removing the invasive tree species, planting more oak species and prairie grasses, and carrying out fires to control the density of vegetation.

Three-Year Analysis of the Habitat of the Henslow’s Sparrow Compared to Randomly Selected Grassland Areas. VIRAG NANAVATI (University of Illinois at Chicago, Chicago, IL, 60527) ROD WALTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

Henslow’s Sparrows (Ammodramus henslowii) are endangered prairie birds, and Grasshopper Sparrows (Ammodramus savannarum) are rare birds in Illinois. Historically, grasslands throughout the state provided these birds with a suitable habitat. However, due to the loss of grasslands, the population of these birds is declining. This longitudinal study is being conducted to improve understanding of the habitat preference of the Henslow’s Sparrow and Grasshopper Sparrow. This, in turn, will help the Fermilab land managers to develop a restoration plan. In this study, we found Henslow’s Sparrows at twenty-three sites and found Grasshopper Sparrows at two sites. Due to such a small sample, the Grasshopper Sparrow’s data was not analyzed. A vegetation survey using the point-quarter study methodology was done at each bird location. The emphasis of the vegetation survey was to characterize the general physical structure of the habitat rather than studying the exact species of plants. Random quadrats near each nesting site were surveyed for maximum plant height and duff height. Visual estimates were also carried out to determine the average vegetation height, percent of grass, forbs, bare ground, and duff. A similar vegetation survey was also carried out at sixteen random sites on the Fermilab campus to serve as a control. Statistical analysis found that Henslow’s Sparrows are very particular about their habitat. They prefer an average maximum plant height of 90-100 cm, an average plant height of 40-55 cm and average duff height between 4.5-7.5 cm. The Henslow’s Sparrow is also particular about the ground cover in its habitat. It prefers ground cover ranging from 45%-60%, forbs cover from 15%-25%, duff cover that ranges around 25% and minimal bare ground. From the data during the three years of this study, the Henslow’s Sparrow’s consistent preference of habitat has become clear.

Vibration Analysis of a Cryocooler for CDMS. LAUREN COUTANT (University of Illinois, Champaign-Urbana, IL, 61820) DAN BAUER (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

A new pulse tube cryocooler was obtained by the Cryogenic Dark Matter Search (CDMS) research group with the intent of replacing their Gifford-McMahon cryocooler which is currently installed at their research site in the Soudan Mine. A study was done on the new cryocooler to determine its vibration spectrum. More analysis needs to be completed to accurately compare the two cryocoolers, but it appears that the new pulse tube system has less intense vibrations. In addition to measuring vibrations, vibration reduction methods were investigated. Installing flexible materials in the cryocooler is the reduction method recommended for the CDMS project.