“Verifying Einstein”

1. “VerifyingEinstein” UIC QuarkNet Presents: Charlotte Wood-Harrington Bozena Suwary

2. The QuarkNet team of the University of Illinois at Chicago: Chicago Public Schools: Elgin Community High Schools: Clayton Smith Jacqueline Barge Lynn Frosig Jozefa Kondratko Waclaw Kondratko Charlotte Wood-Harrington Proviso Township High Schools: John Beatty Nicholas Guerrero Robert Hurley Harvey Nystrom Bozena Suwary Maine Township High Schools: Katherine Seguino Phil Sumida Rich Township High Schools: Anthony Marturano Faculty Advisor: Mark Adams, Ph.D.

3. Cosmic Rays • Muons are created when highly energetic particles—mostly protons—from deep space collide with atoms in the Earth's upper atmosphere. • The initial collisions create pions (predicted by Hideki Yukawa in 1934) which then decay into muons.

4. “Who ordered that?” (I.I. Rabi) • Muons are particles that are similar to but about 200 times more massive than an electron. • The muon has a measured mean lifetime of about 2.2μs. • If the muons travel at nearly the speed of light then the distance traveled in a typical lifetime will be: d = (2.2 x 10-6 s) ( 3 x 108 m/s) • A distance of about 660 m.

5. Pit Newton vs Einstein Conducted muon mean lifetime studies Sears Tower Compensated for thickness of atmosphere Shielded equipment from RF noise What we did

6. Cosmic Ray Telescope for Sears Tower Rates Cockroft- Scintillator Walton Photo Multiplier Tubes Scintillator Fermi Lab Controller Board HV Boards Scintillator End View Side View muon Signal Cable Aluminum Shield HV cable Serial Line Output Wood Support

7. Cosmic Rates on the Ground 3-fold rate = 158 muons/minute

8. The Sears Tower is 443 meters (1,450 feet) high Muons with a mean lifetime of about 2 ms can only travel about 660 m. Nground = NSears e-t/t Nground = 0.51 NSears Newtonian Calculations

9. g = 1/( 1 - v2/c2) where v is the velocity of the particle and c is the speed of light. The Lorentz factor is given by: RelativityCalculations ∆tEarth = ∆tmuon /sqrt(1-v2/c2) This factor is E/m > 3GeV/0.105GeV = 30 !! So, Nground = NSears e(-t/ γτ) Nground = 0.98 NSears

10. 19th vs 20th Century Physics(How Times Change) Predicts half the number of muons remain at the bottom of Sear’s Tower Predicts about the same number of muons at the bottom Sear’s Tower

11. Rode up 3 elevators to 106th floor Climbed to roof (109th floor) Sears Tower Experiment

12. A Serious Problem • RF noise 10x muon signal

13. The Solution

14. Aluminum foil eliminates RF noise The data collection begins All Smiles After 1.5 Hours

15. Taking Care of Business

16. Data Collection

17. The Art of Teaching

18. And The Winner Is….

19. Analysis Back Home

20. Corrections to Data • Muons slow down (lose energy) going through material. • Take Iron to Sears to fake 1440’ of air • Correct for amount of air (changes in density) • Air (took <8 cm of Iron with us – not quite enough) • STP ( Fe density is constant but air density changes) • Temperature 32C compared to 20C >> +4% • Pressure 1018 hPa compared to 1013 hPa >> +0.5% • Change of air pressure from Sears top to ground pSears/pground = 0.947 implies –2.6% correction • All effects P+T on density = -2.1% and –4% = -6% • Instead of 89 MeV energy loss we expect 84 MeV, so we would expect 166 muons/min (rather than 165)

21. Our Data Results

23. Relativity Reigns

24. Grateful thanks to our outstanding Physic’s Guru and MentorMark Adams, Ph.D.

26. Muon Lifetime at top of Sears Tower about2.5ms

27. Our Calculated Muon Decay Time Using Web-Controlled Continuous DAQ Counter 2 only with C1.C2 trigger 70K events All 3 Counters 400K events

28. Sears Tower Experiment • Einstein’s Time dilation demonstrated - • Muons live 2 ms. Many of them should decay before the ground. • Traveling at c (3x108m/s), they only go 600 m (in one lifetime) before decaying – Sears is 439 m tall • N = N0 e-t/t , so Nground =NSears e-439/600 = 0.48 NSears • We measured almost 1.0, not 0.48 for Nground/ NSears! • Answer is due to time dilation. We measure a longer muon lifetime because it is moving with respect to us. • DtEarth = Dtmuon /sqrt(1-v2/c2) • This factor is E/m > 3GeV/0.105GeV = 30 !! • (Expert comments 1. Muon sees 2.2ms lifetime, but a smaller Sears Tower, 2. Our technique only measures t for muons that stop, so we always measure 2.2ms)

29. A particle moving at close to the speed of light should have a mean lifetime of gt instead of the rest lifetime t . The factor g is called the lorentz factor and is given by g = 1/( 1 - v2/c2) where v is the velocity of the particle and c is the speed of light. Particle physicists are more likely to work in terms of particle energies rather than velocities and it is useful to derive a value of the lorentz factor from the energy of the particle rather than its velocity. The muons are depositing a couple of MeV of energy per cm of scintillator. We have about 8cm of material, so that is 20MeV. The reason so few muons stop, is that they have approximately 4 GeV (ie 200 times as much) of energy. They have that much energy because those muons are the ones that are going so fast that the magnetc field of the Earth does not repel them. They are the ones that can point toward the ground. There are energy levels of the atoms that get excited by the collisions with the muon as it goes through the scintillator. The blue glow is due photons with about 1 eV of energy. Einsteinian Calculations

30. Muon Lifetime atop the Sears Tower