They must be eternal optimists. How else would you explain the plan by physicists to look for a hypothetical particle, the Higgs boson, by sifting through the remnants of an evaporating mini black hole, which itself may or may not exist?
The Higgs boson, which is thought to give all other particles their mass, was first proposed in the 1960s, but has so far escaped detection. One of the primary goals of the Large Hadron Collider (LHC), the particle accelerator being built at CERN near Geneva, Switzerland, will be to search for the Higgs in the shower of particles generated when two high-energy proton beams collide. It won鈥檛 be easy. Physicists predict that the Higgs will be created just once in every 10 trillion collisions. With an estimated 800 million collisions a second when the LHC is running, that鈥檚 still just a handful of Higgs a day, so seeing one is a really remote possibility.
This prompted Gouranga Nayak and Jack Smith of Stony Brook University in New York to look for alternatives. Could the Higgs be found, they wondered, in debris left behind by mini black holes, which physicists think could be created in the LHC if the universe has extra dimensions?
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鈥淭he Higgs might be found in debris left by mini black holes, which could be created if the universe has extra dimensions鈥�
Although the chances of making mini black holes are slim, preparations for detecting them are already under way (New Scientist, 23 April 2005, p 38). 鈥淏lack hole production has long odds, but high stakes,鈥� says Ben Allanach, a physicist at the University of Cambridge.
Theory predicts that, once created, a mini black hole would immediately evaporate in a blaze of Hawking radiation, releasing all manner of particles in the process, including the Higgs. 鈥淚t sounds crazy, but if mini black holes can be created then the Higgs must be produced,鈥� says Smith.
What鈥檚 more, if gravity comes into play in particle interactions at energies of a few tera-electronvolts (TeV), as some theories of quantum gravity suggest, then Nayak and Smith鈥檚 calculations show that far more Higgs bosons will be produced by mini black holes than by conventional collisions (Physical Review D, vol 74, p 014007). Energies of a few TeV can be achieved in the LHC.
鈥淭hat鈥檚 exciting,鈥� says Horatiu Nastase, a theoretical particle physicist at Brown University in Providence, Rhode Island, who works on mini black holes. 鈥淣obody suspected that the Higgs signature from black holes could potentially be so large.鈥�
Cigdem Issever of the University of Oxford, who is heading the hunt for mini black holes as part of the ATLAS experiment at the LHC, hopes to spot the fleeting presence of an evaporating black hole by looking for events in which many particles are suddenly sprayed out in every direction 鈥渓ike a firework鈥�. Unfortunately, finding a Higgs in this outburst will be just as problematic as finding one in the aftermath of the collision of proton beams. 鈥淭he real difficulty is identifying the Higgs,鈥� she says. 鈥淲e don鈥檛 know its mass.鈥�
She believes that Nayak and Smith鈥檚 mechanism will work best if used in tandem with the conventional search. So when physicists suspect they have created the Higgs by normal collisions and can estimate its mass, Issever could check whether a similar particle has been produced by a mini black hole.
Issever points out that Nayak and Smith鈥檚 idea could become crucial for finding the Higgs if physicists don鈥檛 find it via normal collisions before the energy of the LHC proton beams crosses the threshold for producing black holes. Past this point, finding the Higgs the conventional way will become impossible. 鈥淥nce black holes are produced, any new particles thrown into the mix will be swallowed by them, so you won鈥檛 be able to study normal particle collision processes,鈥� says Issever. 鈥淚n that case, black hole production will be the only way to make the Higgs.鈥�
Ironically, the detection of a mini black hole would upstage the Higgs boson. 鈥淚t would be the find of the century,鈥� says Allanach. Their presence would confirm the existence of extra dimensions and provide experimental evidence for string theories. 鈥淐reating a mini black hole and then sifting through the rubble for the Higgs would be like discovering America for the first time, and being fascinated that there are daisies there,鈥� he says.
