Cdms veto Stability Study and Calibration Gabriel Caceres

CDMS Veto Stability Study and Calibration

• Gabriel Caceres

• Augustana College,

• Physics Department

• Advisor: Dr. Dan Bauer

First Things First…

• Astrophysics at Fermilab?

• Why yes! There are plenty of astrophysical projects for the advancement of particle physics.

• And what is this CDMS you speak of?

• The Cryogenic Dark Matter Search is one of the world’s leading dark matter experiments!

Outline

• Dark Matter

• CDMS

• Cosmic Background and Veto

• Veto Stability

• Veto Calibration

• Conclusion

Dark Matter

• Gravitational lensing shows that there’s more mass than visible stars.

Dark Matter

• Rotational Curves show that galaxies rotate faster than what is expected from the luminous mass. This also gives us an idea of the distribution of dark matter.

Main Focus:

• Main Focus:

• Weakly Interacting Massive Particles (WIMPS)

• Non-Baryonic
• Relics from the early universe
• Don’t interact with the electromagnetic or the strong force
• May interact weakly with an atomic nucleus
• Supersymetric WIMP candidate: Neutralino

Solid state detectors to observe WIMP nuclear recoil.

• Solid state detectors to observe WIMP nuclear recoil.

• Detect phonons created by lattice vibration from collisions with the Silicon and Germanium nuclei.

Phonon-Ionization ratio to distinguish nuclear and electron recoils.

• Phonon-Ionization ratio to distinguish nuclear and electron recoils.

• Detectors need to be cooled to mK scale for phonon sensitivity.

• Sensitivity to signals of a few tens of keV.

Cosmic Background and Veto

• Cosmic showers are created by particles from space interacting with the atmosphere and matter on Earth.

• Dark matter experiments have been led underground to avoid these cosmic background effects.

Cosmic Background and Veto

• Rock deep underground reduces cosmic ray rate by ~105, but the rate is still high enough to affect the detectors.

• In other words, while 1 muon per second passes through your hand at the surface, 1 muon per minute passes through the whole veto system down in the mine

Veto Stability Study

Veto Calibration

As a test to the calibration run, we compared the Co peak with the WIMP search data, where we expected to see background Co and K in the mine.

• As a test to the calibration run, we compared the Co peak with the WIMP search data, where we expected to see background Co and K in the mine.

Veto Calibration

Veto Calibration

• We expect the veto trace peak finding algorithm to pick up peaks of 16.67 ±6 ADC.

• Using the linear correlation determined previously, we found the minimum energy that can be recorded by the top veto panels to be:

Conclusions

• To maximize sensitivity and the chances of discovering dark matter, experiments have to go underground to reduce cosmic background.

• CDMS has a passive Polyethylene and Lead shield as well as an active scintillator veto to reject any remaining background.

• To obtain the best results, it is necessary to understand the response and capabilities of the veto.

• Veto response was deemed stable to 3%.

• Average minimum energy detectable by the veto panels is .71 ± .1 MeV.

Acknowledgments

• My advisor, Dan Bauer, for all his help and support as well as taking me to Soudan to work on my ping pong skills.

• All of the Fermilab CDMS group who were a great help. Particularly Jonghee Yoo and Jeter Hall who I worked closely with.

• Fermilab and the SIST program for the opportunity to be here today.