Fermi National Laboratory

Volume 26  |  October 2003  |  Number 14
In This Issue  |  FermiNews Main Page

Fermilab Today Launches Result of the Week
Fermilab's daily online news service, Fermilab Today, launched a new weekly feature on September 18—the Fermilab Result of the Week. Each Thursday, FT will bring readers a new scientific result from ongoing research at Fermilab. The inaugural story featured two results, one from CDF and one from DZero, both focusing on the fascinating search for extra dimensions beyond the familiar three of space and one of time. Future Thursdays will bring more forefront results from the collider collaborations as well as from neutrino experiments, astrophysics and accelerator physics research. Fermilab Today

You can subscribe to Fermilab Today at www.fnal.gov/today/.

DZero: Particle Pairs and Monojets

The hypothesis of extra dimensions in space large enough to be detectable by existing or near-future experiments is by far the most revolutionary attempt to solve the hierarchy problem of the Standard Model. No wonder it has captured the public's imagination and inspired experimentalists around the world.

In 2000, DZero pioneered searches for extra dimensions at proton colliders by looking for anomalies in the production of pairs of electrons and photons due to the effects of gravitational interaction amplified by extra space. Two years later DZero was first to look for production of "monojets"—single remnants of a quark or a gluon recoiling against the invisible graviton disappearing in extra dimensions.

Now, with the higher energy of the Tevatron and more data, DZero continues the quest. In the new result unveiled at Lepton-Photon 2003, DZero has extended the search by looking for pairs of electrons, photons, and muons and set the most stringent limits on their existence to date.

While no evidence for extra space has been found so far, we plan to increase our sensitivity by another factor of two in the next three years.

 

CDF: The Bulk and The Brane

We may live in a world that has more than the usual four dimensions (one time dimension + 3 space dimensions) of our everyday experience. Indeed, one way to explain the peculiar properties of gravity is that the universe extends in 4+n dimensional space (the bulk) while we are trapped in the familiar 4 dimensional world (the brane).

Our web site illustrates a proton and antiproton colliding in the brane to send a graviton out of the brane, carrying away energy and momentum. We observe the "missing energy" signature of this escaping graviton (called a Kaluza-Klein particle), similar to the way the existence of neutrinos is inferred in collider experiments.

The result of our analysis is to constrain at 95% confidence level the value of the effective Planck Scale for 2,4, and 6 extra dimensions to be greater than 1 TeV, 0.77 TeV, and 0.71 TeV, respectively, the best result from a direct graviton emission search at the Tevatron.

Note that the Tevatron is now running at a higher energy (approximately 2 TeV) and that we will soon have many times the data sample analyzed here. This will make us sensitive to an effective Planck Scale as high as 1.5 TeV for two extra dimensions.



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