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Large Hadron Collider Particle Speed At Collision

10/16/2014 6:10 AM

As I understand it, at the most basic level, the LHC accelerates particles to the speed of light (or nearly so) in two parallel opposing paths.

At the critical moment the paths are made to cross each other causing the particles to collide - when the 'broken' bits are studied - one of which is hopefully a Higgs boson.

My basic question is related to the approaching speed of the particles at time of collision - which on the face of it 2 x light speed.

But is it?

Just curious.

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#1

Re: Large Hadron Collider particle speed at collision

10/16/2014 6:44 AM

Well, all it matters, is the collision energy, that has the potential if high enough, to "brake" known particles to something more elementary. Absolute and relative between particles speeds, are, well, both relative. Inconsistencies to Newtonian predictions is what lead to relativistic extensions in the first place. If you were hypothetically riding the back of the accelerated particle, approaching relativistic speeds (according to an external observer) your inertial time (and perception of it) having slowed (according to relativity), then, if you had a police speed radar handy that wouldn't have to obey relativity limits, yes, it would show opposite particle approaching you at 2C, and you both should be fined for exceeding light speed limit. It's just that you won't find such a radar. S.M.

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#2

Re: Large Hadron Collider Particle Speed At Collision

10/16/2014 11:45 AM

No, the particles do not collide at a relative velocity to each other of 2c. The space/time distortions keeps things below c.

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#3

Re: Large Hadron Collider Particle Speed At Collision

10/16/2014 2:15 PM

No. The sums don't work that way. The total relative velocity is always less than c for particles that have rest-mass and exactly c for particles that don't.

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#4

Re: Large Hadron Collider Particle Speed At Collision

10/16/2014 11:54 PM

I think that was an interesting question myself. Although considering that neither particle is actually traveling faster than the speed of light, then I would say nothing is breaking that speed limit. But then you have to wonder about the particles being ejected.

Anyway it's pretty interesting stuff. It amazes me what science can pull off

And btw, I was reading this article about the gigaelectronvolt (GeV) while looking in to this stuff. It appears they're actually describing the mass of these particles increasing during the process rather than concentrating on speed.

Here's an article that directly asks the same question the OP asked as well.

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#7
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 4:45 AM

For the past 2 years we have been working on the next generation of detectors for the collider (LHCb) & have been involved in 2 other projects there. Just building the 1st prototypes now.

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#15
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 1:49 AM

I'm going to get into a lot of trouble for posting this because everyone has been pointing out the fact that combining speeds of the two high energy particles don't bring about anything that would be considered a speed faster than light, and so I'll mark it off topic. But I'm going to go ahead and say it anyway because you mention working on some new detecting equipment. Now knowing that scientists have the ability to detect things down to nanoseconds or greater, how about setting up one detector that is perfectly in sync with the timing of another. The first would be used to detect and record the exact time of the particle's collision. And the other would be setup to detect and record the exact time of the first detected emission from the collision. Now if I'm not wrong, and there is faster than light speeds involved, the second detector should record an instance time that actually takes place before the collision. What do you think :-)

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#16
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 9:22 AM

I think you're making one of the most common misunderstandings about relativity. Time is not constant, or put another way, time changes depending on how fast one slices through space-time. This aspect is what generates the twin paradox.

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#19
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 6:50 PM

I read the Twins Paradox' link. Thanks. As a follow-up, although the ships 'clocks' and Earth 'clocks' run at their 'own' times, would each human body age by it's own internal clock or the actual clock

Would the difference in body ages be apparent to each of the twins when they met?.

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#20
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 10:18 PM

It is each twin's actual time frame that moves at their own time. If the time difference is 40 years then one twin will be 40 years older when they meet again.

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#21
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Re: Large Hadron Collider Particle Speed At Collision

10/19/2014 6:43 AM

Hello Redfred. Thanks, (I'm puzzled why your reply has been marked 'off-topic' ? - it certainly isn't), anyway what I had in mind when I posed the supplementary question was about the appearance of the twins age.

Would the 40 year old twin actually look like 40 years old, or vice-versa, the other twin look 40 years younger. ???

PS thanks to all contributors, your help is appreciated.

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#22
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Re: Large Hadron Collider Particle Speed At Collision

10/19/2014 7:53 AM

No, time still moves forward for both twins. Here is the twins paradox of Bob and Bill starting at age 20.

Bob stays on Earth while Bill goes on a relativistic travel to Alpha Centauri and back. Bob is told that the next time he sees Bill will be in 50 years when Bob is 70 years old. When Bill meets Bob again, Bob is enjoying his retirement having lived a good life with 50 years of stories to tell. Bill instead is only 30 years old. Bill has just completed his first interstellar journey of his career and has just ten years of stories to tell about six months exploring the Alpha Centauri binary system and nine and a half years of life on a near light speed spaceship.

As for the OT rating, this relevant tangent started as an OT designation.

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#23
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Re: Large Hadron Collider Particle Speed At Collision

10/19/2014 3:39 PM

There will actually be, I think, 100 detectors at the LHCb position. We don't know yet how fast these detectors will be but others that we make work in the femtosecond range. I think the question of speed has been answered by others but whatever detector we make, it can only work at the speed of the electrons that power it. For instance, in our 25mm photon detectors, the speed is limited by the time it takes electrons to travel from the outside of a 25mm circle to the centre. We currently achieve at best 3-5ns switching speeds.

Whatever is detected at CERN, most of the theories & answers will come from the work of the physicists & other scientists using evidence gathered by the detectors.

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#24
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Re: Large Hadron Collider Particle Speed At Collision

10/19/2014 7:19 PM

Do they accommodate such delays even so? The signal arrives 'late' compared to other signals from faster detectors, but if you know the latency (and if it's fairly constant) then you can time-correlate your signal with those others, yes? Is this an option?

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#25
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 6:15 AM

The detectors are a bit of a 'shotgun' approach, the event is over very quickly & the detectors try to record everything in that instant. You can read more about LHCb here, a lot of it is over my head.

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#26
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 6:41 AM

The aim of the LHCb experiment is to record the decay of particles containing b and anti-b quarks, collectively known as 'B mesons'. The experiment's 4,500 tonne detector is specifically designed to filter out these particles and the products of their decay.

Rather than flying out in all directions, B mesons formed by the colliding proton beams (and the particles they decay into) stay close to the line of the beam pipe, and this is reflected in the design of the detector. Other LHC experiments surround the entire collision point with layers of sub-detectors, like an onion, but the LHCb detector stretches for 20 metres along the beam pipe, with its sub-detectors stacked behind each other like books on a shelf.

In which part of the detector are your products used? What kind of detector elements? You mentioned once that you worked with PMTs (did your question get answered about the housing material in that thread, btw? I don't recall. It's been awhile and I'm going senile ).

I seem to recall that those hadron-bunches collide about 11,000 times per second, but the individual event rates are far, far higher. What is the recovery time of your detectors? A couple a nanoseconds' latency is one thing - it's simply a delay in the 'pipeline' - but a long recovery time and you miss events alogether because the detectors are 'blind' during this time. Is this the issue?

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#27
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 6:59 AM

The detectors will be in a ring around the pipe, not sure exactly where. The front of the detector will be a quartz window, the housing probably just an epoxy encapsulant.

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#28
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 7:24 AM

Are they PMTs? Microchannel plates?

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#29
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 7:29 AM

Yes & yes, Gen.2 PMTs.

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#30
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 7:42 AM

Ah!

Those femtosecond-range detectors must be quite small to get those speeds. Electron mobility/flight times and all that. That damned c again.

The signals from detectors in various locations at the experiment will arrive for processing at different times depending on the distance they have to travel, so what did the designers do? Insert calibrated delays to even everything up? Something as simple as pieces of coax cut to length, tailored for each detector so that all the signals arrive as an ensemble? How do they address the timing issues of multiple detectors there? Some of those experiments must have thousands of detector elements distributed over a large volume.

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#31
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Re: Large Hadron Collider Particle Speed At Collision

10/20/2014 7:53 AM

From the detector surface to the MCP we will aim at about 50-100um. The anode can be a bit further away, probably a few mm.

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#13
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 2:35 PM

Yes, it is quite common to see particle mass expressed in terms of energy. The rest-mass of an electron, for instance, is slightly less than 511 keV - around half the energy you'd get if you brought an electron and a positron (an anti-electron) together (slowly), annihilating them to produce a flash of gamma rays and neutrinos.

What lets physicists 'get away with it' is that Nature herself makes no distinction between mass and energy. To her they are simply different forms of the same thing, 'mass-energy.' That's what the equals-sign in E = mc2 means: when it comes to making distinctions between mass and energy, Nature herself couldn't care less. To her there is no difference; none at all.

"Those are Man's distinctions, not Mine. Glad you finally saw the light, btw, but please don't abuse it."

Oops. Too late.

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#5

Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 12:06 AM

Einsteins theory stipulates that nothing can travel faster than the speed of light regardless of the relative velocity of the observer. This means that an observer standing on the ground between the two particles sees each particle travelling towards him at almost the speed of light while a (hypothetical) observer travelling with one of the particles sees the other particle as travelling towards him at a faster speed than the ground observer but still slower than the speed of light.

The formula for the velocity of particle 2 as seen by a person travelling with particle 1 is ((velocity of particle 1)+(velocity of particle 2))/(1 + ((velocity of particle 1 X velocity of particle 2)/(speed of light squared))).

Assume both particles are travelling at a speed of 0.9c (0.9 X speed of light) towards each other (as measured by a stationary observer on the ground). Using the above formula gives (0.9+0.9)/(1 + (0.9X0.9)/1) = 1.8/1.81 = 0.994c as the speed that an observer travelling at the same velocity as one of the particles would measure the speed of the other particle.

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#6
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 12:18 AM

Wow. As simple as it was, that formula just blew my mind. GA lol

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#9
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 8:58 AM

In the application of the formula

[ (0.9+0.9)/(1 + (0.9X0.9)/1) = 1.8/1.81 = 0.994c ]

in the second half of the left expression, where it reads in part X0.9)/1) how did that come out to 1.81(c)?

I'm assuming you left out the closing right paren in your second expression on the left side, i.e., (1 + (0.9X0.9)/1) )(added by me), without which it doesn't evaluate at all. But if it should be as I've shown it, then this expression evaluates to (1+(1.8)/1) equals 1+1.8 equals 2.8.

What did I miss?

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#10
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 11:32 AM

With

as reference, and where, in his example

v and u both equal 0.9c, we've got

s = (0.9c + 0.9c) / [1 + (0.9c * 0.9c / c2) ]

s = 1.8c / [1 + (0.81c2 / c2) ]

s = 1.8c / 1.81

s = 0.99(44..)c .

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#12
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 1:20 PM

Thank you. Stupid struck. Clarification (and knowledge struck harder) (and, probably, just in time).

I'll try to duck quicker next time stupid comes tooling along.

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#14
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Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 10:06 PM

Lol! Gawd I hate it when that happens - and it happens a lot more these days. That or I'm simply more aware of it. Either way it can be pretty discouraging!

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#17
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 2:11 PM

My wife says I'm getting older. She's right. We all are. Rats!!

And I tried Sooo hard!!!

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#18
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Re: Large Hadron Collider Particle Speed At Collision

10/18/2014 2:16 PM

At the rate of sixty seconds per minute - and sometimes faster (depends on how much fun you're having versus the inlaws coming over for an extended stay. Mine did that for a year one week. It's all relative. )

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#8

Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 8:01 AM

You needn't even invoke something so exotic as the LHC to get such conditions of relative speed, and you can do it on your own kitchen table - just aim two flashlights at each other!

The particles from each one - photons - are travelling at at even higher speeds (c) than the ones in the LHC (because photons don't have rest-mass) relative to their flashlight, so what is the sum of the photons' speeds relative to each other? It is also c.

It's not intuitive at all, but it's true nonetheless - and took an Einstein to first figure out why. The sums of relative speeds of physical objects - any physical objects; photons, protons, cars, spaceships, you name it - never exceed c. Ever.

Moreover, it is not the 'speed of light' *itself* that is the limit, btw, in spite of the term's popular usage. Light just happens to travel at that same speed, c. More fundamentally it is the limit on how fast *information* can travel. Quantum mechanics, for example, describes certain systems whose (entangled) components superficially appear to violate this speed limit, but even in these systems no information is actually being exchanged faster than c. It is truly a fundamental speed limit.

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#11

Re: Large Hadron Collider Particle Speed At Collision

10/17/2014 12:01 PM

Einstein had afterthoughts of calling his theory of relativity, "Invariantentheorie". Invariant mass is a measure of total energy. It tells you how much mass can be created from the energy imparted in the system. If a system has no momentum, E=mc2 applies. So knowing the energy at rest is equivalent to knowing its invariant mass. If you have two beams with the same energy collide, they will have equal and opposite momentum. At the point of impact, the added momentum of the two particles will be zero. So all the energy in the two particles will now be converted to mass. I guess that is the aim of colliders so they can identify particles.

Now suppose you had a single beam and a sitting duck target with zero momentum. Not all the energy is available to make new particles. It turns out that if we increased the energy in the moving particle we would only get back the square root of the energy. By placing two moving beams on a path to collide we do not simply get twice the energy . That would be Newtonian thinking. The two beams will collide with much higher energy because of the relativistic theory.

The speed is the problem of thinking in Newtonian terms. Remember it is the energy imparted to the mass that will limit the speed. The amount mass all be converted to energy at the speed of light is approached and therefore have the mass gets smaller. It really never reaches the C. It is a limit on the speed so to speak. Consider yourself on the particle approaching another particle travelling at your same speed near the speed of light. Your speed relative to the approaching speeding particle will always be less than the speed of light. Read Lisa Randall, Knocking on Heavens Door .

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#32

Re: Large Hadron Collider Particle Speed At Collision

10/21/2014 9:41 AM

We are trying to break a Higgs boson ??

My vocabulary is broken.

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