Comments on: Single top observation – when ? http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/ private thoughts of a physicist and chessplayer Thu, 24 Dec 2009 08:50:26 +0000 http://wordpress.com/ hourly 1 By: dorigo http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-650 dorigo Sun, 11 Jun 2006 20:06:46 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-650 I think single top production has the potential of yielding a measurement of Vtb of some significance only at the LHC, and even there, not terribly so. In the SM these processes occur by force and it is not too interesting to find them. More interesting would be not to find them! As Alejandro points out, a whole set of theories would take the stage. So, as experimentalists, we should finish the job with the top quark, and show it behaves as we expect it does. Cheers, T. I think single top production has the potential of yielding a measurement of Vtb of some significance only at the LHC, and even there, not terribly so.
In the SM these processes occur by force and it is not too interesting to find them. More interesting would be not to find them! As Alejandro points out, a whole set of theories would take the stage.
So, as experimentalists, we should finish the job with the top quark, and show it behaves as we expect it does.

Cheers,
T.

]]> By: Michael Schmitt http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-645 Michael Schmitt Sun, 11 Jun 2006 17:56:50 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-645 Hi Tommaso, I'll bet that you're right, and CDF & D0 find the first evidence for single-top production at the Tevatron. As you point out, this is quite difficult for experimental reasons, and requires a lot of data. One question I have, though: why would you, personally, find a positive result for this interesting? There are theoretical and experimental reasons, but what is the most relevant, in your opinion? Michael Hi Tommaso,

I’ll bet that you’re right, and CDF & D0 find the first evidence for single-top production at the Tevatron. As you point out, this is quite difficult for experimental reasons, and requires a lot of data. One question I have, though: why would you, personally, find a positive result for this interesting? There are theoretical and experimental reasons, but what is the most relevant, in your opinion?

Michael

]]> By: dorigo http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-632 dorigo Sat, 10 Jun 2006 16:26:21 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-632 Good question... If you ask how long it will take CDF and D0 to exclude single top production, I think it will take a couple more years of running to say it for sure (95% cl exclusion limits below the SM prediction mean nothing to me - once in twenty times they are wrong!). It would be puzzling... and fun! Cheers, T. Good question… If you ask how long it will take CDF and D0 to exclude single top production, I think it will take a couple more years of running to say it for sure (95% cl exclusion limits below the SM prediction mean nothing to me – once in twenty times they are wrong!). It would be puzzling… and fun!
Cheers,
T.

]]> By: Alejandro Rivero http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-622 Alejandro Rivero Fri, 09 Jun 2006 22:11:12 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-622 Hmm, and if a single top is not seen... how many time will be take to have "new physics at five-sigma deviations" for this particular reaction? I am thinking on the models where symmetry breaking comes from a composite of top+bottom or top+newcolouredthing. The b-t-W vertex should be affected by this new physics. Hmm, and if a single top is not seen… how many time will be take to have “new physics at five-sigma deviations” for this particular reaction? I am thinking on the models where symmetry breaking comes from a composite of top+bottom or top+newcolouredthing. The b-t-W vertex should be affected by this new physics.

]]> By: dorigo http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-621 dorigo Fri, 09 Jun 2006 20:22:00 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-621 Hi Fred, no, no supersymmetry at work here. In the Standard Model, Baryon number violation is actually allowed, although with extremely low probability and at very low energy. Baryon number violating processes in the SM are associated with a quantum-mechanical effect called "tunnelling", whereby an exponentially decaying spatial amplitude for a wave function maintains a non-zero value through an energy barrier, and - if the barrier is narrow enough and not high enough to make the wave function really vanishing - the wave function has a chance to "pop out" of the barrier, tunnelling away from the trap. Not clear enough, huh ? Ok. Imagine a quantum well. It is a region of space where the potential energy of a particle is smaller than its total energy. Thus, the particle has some kinetic energy left, and it propagates within the region. Now, if you take the quantum-mechanical description of the particle as a wave propagating in the well, this is a wave function. A function that describe the "amplitude" for the particle to be in any particular spatial point within the well. Within, and outside of it. In fact, if the height of the "walls" is not infinite, the wave function "leaks" outside of the well and inside the walls, with an exponentially vanishing amplitude. It is as if the particle has a extremely small, but non zero, chance of being found inside of the walls. Now, if the walls are not thick enough, this exponential tail of the wave function will extend past the wall. Past it, the particle described by that tiny amplitude that has leaked out of the wall will have again a positive kinetic energy, and it will be perfectly legal for it to propagate there. The particle has "tunneled" inside of the wall and out of the well. I think I will post about this effect in my blog... Just allow me some time to recover from tonight's soccer game - I'm exhausted! Cheers Tommaso Hi Fred,

no, no supersymmetry at work here.

In the Standard Model, Baryon number violation is actually allowed, although with extremely low probability and at very low energy.

Baryon number violating processes in the SM are associated with a quantum-mechanical effect called “tunnelling”, whereby an exponentially decaying spatial amplitude for a wave function maintains a non-zero value through an energy barrier, and – if the barrier is narrow enough and not high enough to make the wave function really vanishing – the wave function has a chance to “pop out” of the barrier, tunnelling away from the trap.

Not clear enough, huh ? Ok. Imagine a quantum well. It is a region of space where the potential energy of a particle is smaller than its total energy. Thus, the particle has some kinetic energy left, and it propagates within the region. Now, if you take the quantum-mechanical description of the particle as a wave propagating in the well, this is a wave function. A function that describe the “amplitude” for the particle to be in any particular spatial point within the well.
Within, and outside of it. In fact, if the height of the “walls” is not infinite, the wave function “leaks” outside of the well and inside the walls, with an exponentially vanishing amplitude. It is as if the particle has a extremely small, but non zero, chance of being found inside of the walls.
Now, if the walls are not thick enough, this exponential tail of the wave function will extend past the wall. Past it, the particle described by that tiny amplitude that has leaked out of the wall will have again a positive kinetic energy, and it will be perfectly legal for it to propagate there. The particle has “tunneled” inside of the wall and out of the well.
I think I will post about this effect in my blog… Just allow me some time to recover from tonight’s soccer game – I’m exhausted!

Cheers
Tommaso

]]> By: Fred Altieri http://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-620 Fred Altieri Fri, 09 Jun 2006 15:20:29 +0000 https://dorigo.wordpress.com/2006/06/09/single-top-observation-when/#comment-620 Tomaso, I've read, "The law of the conservation of baryon number states that the total number of baryons must be the same before and after any subatomic event." Is this a supersymmetrical condition "thus guaranteeing the stability of baryonic matter?" Thanks for your patience, Fred Tomaso,
I’ve read, “The law of the conservation of baryon number states that the total number of baryons must be the same before and after any subatomic event.” Is this a supersymmetrical condition “thus guaranteeing the stability of baryonic matter?”
Thanks for your patience, Fred

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