The Standard Model prevails—so far: CMS experiment publishes first test at new LHC energy of 13 TeV

The Standard Model prevails – so far
A top quark candidate in the CMS detector. Credit: CMS Collaboration

Shortly after the start of Run 2 at the Large Hadron Collider (LHC) at CERN in June 2015, scientists from DESY and their colleagues from the experiments CMS and ATLAS have performed a first important test of the Standard Model of particle physics at the new energy frontier, using data from proton-proton collisions at higher proton beam energies than ever achieved before. They looked at the production rate of a well-known particle called the top quark to see if it behaves differently at higher collision energies. Their study shows: it doesn't.

Top quarks are the heaviest and among the most puzzling elementary particles. They weigh even more than the Higgs boson discovered in 2012 and might have a special connection to it. To analyse this relation and to test if the top quark is exactly the particle predicted by the current theory, physicists at the LHC perform high-precision measurements of the properties of the top quark. One of the most exciting studies to that respect is to measure the production rate, or , for top quark pairs in the new energy range never explored before because it provides an excellent test of the Standard Model and might give scienists a first glimpse of new physics beyond.

DESY scientists led the effort to measure the top quark pair production cross section at a proton-proton collision energy of 13 TeV. "The results are in good agreement with what we expected. This is a another huge success of the Standard Model," said Alexander Grohsjean from DESY's CMS group. The results are presented and discussed this week at the international high energy physics conference "XXVII International Symposium on Lepton Photon Interaction at High Energies".

The Standard Model prevails – so far
Top quark pair production cross section measurements compared to the Standard Model predictions as a function of the center-of-mass energy. The new result of the CMS collaboration at 13 TeV is displayed in red and is in agreement with the theory prediction (green band). Credit: CMS Collaboration

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Aug 21, 2015
Poor Tevatron! It can do 2 TeV, while LHC is the real TeV factory...

So, almost twice the energy and not a twitch from the Standard Model.

Aug 21, 2015
Can anyone explain to me why the mass of the top quark is so much massive than the proton which contain's one? From what I understand the proton's mass is 938 mev while the top quark has a mass of 126 gev.

Quote from article:
"Top quarks are the heaviest and among the most puzzling elementary particles. They weigh even more than the Higgs boson discovered in 2012 and might have a special connection to it. To analyse this relation and to test if the top quark is exactly the particle predicted by the current theory, physicists at the LHC perform high-precision measurements of the properties of the top quark."

Read more at: http://phys.org/n...html#jCp

Aug 21, 2015
bill: E=mc^2 tells us we can turn energy-of-motion into energy-of-mass. When we collide nuclei (including lone protons), occasionally some of the energy of motion from one nucleus with respect to the other will go into producing a top/anti-top pair of quarks.

Aug 21, 2015
There are only two particles, +&-!

Aug 21, 2015
Theory has become pontification, not physics or logic. More like visions of magic. We use EM fields to measure, all causal from the simple +&-. A unified set of field equations must first understand the blunder of a misunderstood constant, m; not a viable unit. Hence, we have a unified set of field equations when we realize that mass, or the measure defined by gravity is the measure of acceleration is proportional to 1/r^2 defined by Maxwell using superposition. The error in the universal constants using mass must be reconciled. Dark matter, really? E = MC^2 is incorrect, the number of particles within any containment is always a constant, none are created or destroyed only changes in position and rate of change. Mass is very misunderstood. Only a mass of particles, +&-. A point within a changing field is not necessarily a particle unless it can be isolated and displayed, photons and ... cannot be isolated.

Aug 21, 2015
Shavera, I understand how velocity effects mass, what I don't understand is how the top quark can be more massive than a proton that contains it. Isn't the proton's mass a rest mass? What about the top quark's mass is that not given as a rest mass?

Quoter from link:
"Quarks have an astonishingly wide range of masses. The lightest is the up quark, which is 470 times lighter than a proton. The heaviest, the t quark, is 180 times heavier than a proton -- or almost as heavy as an entire atom of lead.
"So why these huge ratios between masses? This is one of the big mysteries in theoretical physics right now," Lepage said."

Read more at: http://phys.org/n...html#jCp

Aug 21, 2015
The above is something, but is not as defined, only the thoughts of the educated without proper logic or reason, a certain blindness created by the fallacy of PhD programs in theoretical physics accepting theory as fact without hindsight or proper reconciliation with the obvious. Am I the only one that can see this? I'm just an EE, I work with facts and demonstrate fact. I have no problem designing the tools used at CERN and defining the measurements to known science, not some idea from someone from the 20th century that does not really understand that the electron and a proton, +&-, may create a certain stability as a neutron. You would need something like 5..10 newtons to separate the proton from a neutron, within an atom it may be even higher. You may calculate this, "Strong Force" and the instability, the "Weak Force" using only a calculator without smashing protons together.

Aug 21, 2015
There is no need for quarks or dark matter or GR. It's obvious, isn't it time we "recognize." We have a unified theory, a simple 4D unit-less space. The constant, c = lambda nu -> equal units, or numbers mapped into reality. Complete description of every atom, or mass of particles at any instant or point within the 4D space. Only need is a large and fast enough computer to define larger and larger masses. Not colliders required as exploratory tools!

Aug 21, 2015
bill: "...how velocity [affects] mass": Actually, it's far better to only think about one kind of mass. Rest mass. Some people tried to teach relativity as having a "relativistic mass" too, but this isn't a really great way of teaching the topic (Better to say that momentum, p, as p=mv is only *approximately* true, and more approximately correct when v << c.)

One way to look at these kinds of collisions is that within a proton, say, there are "sea quarks." These are virtual particle/anti-particle pairs of quarks that arise from how quantum mechanics behaves. In a collision, you can "transfer" energy into these virtual particles to make them "real."

Aug 21, 2015
Another way is just to look at energy. Let's use a frame where one proton is at rest. before the collision there is energy p + m + m. Momentum plus the two masses of the protons. After the collision there is p + p + p + p + m + m + m + m... Where p is the momenta of both protons, momenta of the top/anti-top quarks, and m the mass of both protons, the top/anti-top quark, plus whatever other ejecta come out of the collision.

So long as the 'p' in that first part of the equation is big enough, that's all that conservation of energy really cares about.

---

Finally, the last way to look at it. Let's use that 'relativistic mass' model I dislike. In the collision, one proton is at rest, and the other flying toward it. But at such high speed, the other's mass looks like 13 TeV, not 900 MeV. So in this case, there's more than enough mass to create top quarks.

Aug 21, 2015
Shavera, I can understand how a high velocity collision between two protons can contain plenty of relativistic energy to create a pair of quarks that are much more massive than the rest mass of the two protons. What I am having trouble understanding how the up quark that is much more massive than the proton can be part of a much less massive proton. Is the mass of the up quark given as a rest mass or a relativistic mass? If it is given in the relativistic mass what would its rest mass be and why would it be stated it is much more massive than the proton?

Aug 21, 2015
Imagine it like having a helium balloon that also has a tennis ball inside. Once you pop the balloon, the tennis ball will weigh many times what the balloon did, and if you ignore the loss of lift from the now missing helium, it doesn't make sense. The photon and Top Quark are like that only the helium is energy balancing out mass. As long as the end result accounts for all of the mass, spin and other energies involved, we should be happy.

Aug 21, 2015
In my previous post I referred the "up quark" I meant to refer to the "top quark". Sorry

Aug 21, 2015
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Aug 21, 2015
Can anyone explain to me why the mass of the top quark is so much massive than the proton which contain's one? From what I understand the proton's mass is 938 mev while the top quark has a mass of 126 gev.

The proton is theorized as consisting of two up and one down quark. A top quark is not involved.

Aug 21, 2015
Shavera, I understand how velocity effects mass, what I don't understand is how the top quark can be more massive than a proton that contains it. Isn't the proton's mass a rest mass? What about the top quark's mass is that not given as a rest mass?

Quoter from link:
"Quarks have an astonishingly wide range of masses. The lightest is the up quark, which is 470 times lighter than a proton. The heaviest, the t quark, is 180 times heavier than a proton -- or almost as heavy as an entire atom of lead.
"So why these huge ratios between masses? This is one of the big mysteries in theoretical physics right now," Lepage said."
FYI a proton is a uud quarks bound state and is the only baryonic stable state. Baryons with heavier quarks have other names and they are not stable.

Another important information for you is that the top quark has never been observed in a bound state. Why? read this: https://en.wikipe...rk#Decay

Aug 21, 2015
Can anyone explain to me why the mass of the top quark is so much massive than the proton which contain's one? From what I understand the proton's mass is 938 mev while the top quark has a mass of 126 gev.

The proton is theorized as consisting of two up and one down quark. A top quark is not involved.

Thanks, I'm just getting my quarks mixed up. I always thought the mass of the quarks in a proton could only account for a small fraction of the proton's total mass

Aug 21, 2015
@billpress11, the thing I find most disgusting about you is your misuse of the name of a person who is not dumb enough to subscribe to the prejudices you do. I hope he comes on here one day and makes you look as stupid as you are for contaminating his legacy with your BS.

Aug 22, 2015
Great that LHC is up and running I wonder for how long since they have to shut it down in November for winter break. As far as confirmation of Standard Model is concerned, they won't find anything new if they are not looking for it and they seem to be happy so far for what they've got, the result based on so far insufficient data.

This is the fate of any "established theory" that cannot be disturbed without disturbing scientific VIPs who have to explain to their sponsors why they spent $30 billion to discover what they already knew before money was spent.

An interesting take on the theory vs reality including peculiar reality of institutional research I found at:

https://questforn...reality/

Aug 22, 2015
This comment has been removed by a moderator.

Aug 22, 2015
This comment has been removed by a moderator.

Aug 23, 2015
Great that LHC is up and running I wonder for how long since they have to shut it down in November for winter break. As far as confirmation of Standard Model is concerned, they won't find anything new if they are not looking for it and they seem to be happy so far for what they've got, the result based on so far insufficient data.

This is the fate of any "established theory" that cannot be disturbed without disturbing scientific VIPs who have to explain to their sponsors why they spent $30 billion to discover what they already knew before money was spent.

An interesting take on the theory vs reality including peculiar reality of institutional research I found at:

https://questforn...reality/

Nonsense.

Aug 26, 2015
Can anyone explain to me why the mass of the top quark is so much massive than the proton which contain's one? From what I understand the proton's mass is 938 mev while the top quark has a mass of 126 gev.

Quote from article:
"Top quarks are the heaviest and among the most puzzling elementary particles. They weigh even more than the Higgs boson discovered in 2012 and might have a special connection to it. To analyse this relation and to test if the top quark is exactly the particle predicted by the current theory, physicists at the LHC perform high-precision measurements of the properties of the top quark."

Read more at: http://phys.org/n...html#jCp

If you look at the superposition of many + charges in close proximity, there exist points with much higher potential. Your measurement of mass is only a measure of potential.

Aug 26, 2015
Once one realizes the failure of the unit mass, one begins to wonder about the size of a sphere that would give an equal volume of a charged particle. Consider what we cannot measure, very high frequencies, we call gamma rays. Define the radiation either as an oscillator or rotary motion. What is the minimum radius? That is, the motion of ejected particles from a nucleus. Are neutrinos for similar ejections the same, why?

Pretty obvious that mass is problematic, denial of this "fact" is bizarre. Something like Bizzarro in Superman comics. Something was wrong with his antithesis. But, hey, let's continue with that!

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