Why hasn't the Higgs boson been detected?

[kab761]

My question is (and it's probably stupid, I'm a layman, please have patience with me): It seems from what I've read that the Higgs boson, if it exists, is very unlikely to have an extremely high mass (above ~500 GeV), and probably has a mass under ~145 GeV. And I know the top quark with a mass of 170 GeV has been produced and detected at Tevatron, 15 years ago. So what is the crucial difference between the Higgs boson and the top quark, that the (presumably lighter) former hasn't been detected and the latter has? I understand some possible issues (it's easier to look for a particle if you can 'tune' your machines to its mass, but the mass of the top quark was unknown too, wasn't it? and you need considerably more energy than the mass of the particle since you will frequently lose energy in forming 'mundane' particles, but isn't this true for any particle, and presumably less so for a less massive one?) but I don't understand what the crucial difference is, why the 14 TeV LHC is needed to look for a 145 GeV particle when the Tevatron was sufficient to find the top quark.

 

[phyzguy]

I had the same question. As I understand it, the simple answer to your question is that the Higgs does not decay in any unique way, so in order to unambiguously find the Higgs, you need to sort through a huge amount of "junk" and apply statistics to prove that what you are seeing is the Higgs and not just the sum of a bunch of other stuff. The top quark decays in some paths that cannot be produced in any other way, so even a small number of events can be enough to say that you have definitively seen the top.

 

[ansgar]

and the top is produced in strong interaction wheras higgs in the weak interaction, so the top production cross section is HUGE compared to Higgs production.

 

[Buster59]

Don't forget that it's still a theoretical particle until its existence has been confirmed.

 

[ansgar]

Don't forget that it's still a theoretical particle until its existence has been confirmed.

yes but according to theory it's properties are fixed functions as it's mass.. which is NOT predicted in theory.

 

[robert2734]

Only the weak force can change flavor and there's no top quark in a proton so isn't top production a weak force interaction? If we have quark+antiquark -> top + antitop, what force is involved?

 

[Parlyne]

Only the weak force can change flavor and there's no top quark in a proton so isn't top production a weak force interaction? If we have quark+antiquark -> top + antitop, what force is involved?

Any of the three forces described in the standard model can do that. But, the dominant contribution is from the strong force. It should probably be pointed out that this process is not flavor-changing. The net flavor of $q\overline{q}$ is 0, as is that of $t\overline{t}$.

 

[ansgar]

Only the weak force can change flavor and there's no top quark in a proton so isn't top production a weak force interaction? If we have quark+antiquark -> top + antitop, what force is involved?

qqbar -> ttbar

or

gg -> ttbar

(g = gluon)

total topness to the left is +1 -1 = 0
total topness to the right is +1 -1 = 0

nice try kid ;)