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i was frustrated by the fact that i couldn t visualize the problems that we were working on i got a better appreciation for curved surfaces by learning to sew and after making about a dozen little models the picture came into focus here is a photo of a model of space time at the surface of the earth in which we can see that a freefall is a shorter path through space time than just standing on the ground it doesn t have minkowski structure so it is not quantitatively accurate it should open up at the top not the bottom but it is a picture to keep at the back of one s mind i ve also turned the spectrum of resonances in electron positron collisions into a sound so that we can hear what it sounds like when the collide and found a nice demonstration of entropy in a story about a leprechaun tying ribbons on trees in a forest if you enjoyed the what killed madame curie detective serial that i started on this blog i am expanding it into a novel with links on the site cheers jim posted in uncategorized 13 comments my last lhc status update september 21 2010 by jim pivarski i haven t said much since this year s start up of the lhc but there have been some interesting developments so i ll add one last update if you haven t been following the lhc status it has been exponentially increasing in collision rate while maintaining a fixed collision energy about 3 pb 1 of 7 tev collisions have been collected by the lhc experiments which is a few thousand times less than the tevatron s 9 fb 1 of 1 96 tev collisions collected since 2001 my particle body counts are now completely obsolete nearly all known particles have been re discovered in the lhc experiments and today the first unexpected effect has been presented by an lhc experiment long range near side angular correlations which is presented in detail on the cms public page below the cut here i ll explain what this means read the rest of this entry tags cms lhc physics posted in basic grad student guests high school undergraduate 11 comments 7 tev collisions tonight march 29 2010 by jim pivarski if all goes well the lhc has been circulating two 3 5 tev beams off and on for the past week and tonight they plan to turn off the separators keeping them apart we should then see the first 7 tev collisions ever produced in a laboratory if there are any undiscovered particles with a mass in the new energy range that is being opened up it would now become possible for them to be spontaneously produced in a detector where we can see them as opposed to cosmic ray air showers our view of particle physics is about to become three and a half times larger than it has ever been the plan at first is just to let the beams collide without focusing them so the luminosity will be low and the rate at which new particles could be produced would be correspondingly low as time goes on the beams will be focused and the intensity will be raised which increases the rate of collisions and therefore the probability of seeing new stuff this is the beginning of an 18 24 month period of continuous data taking and open ended exploration tonight i ll be following this from the fermilab control room the lhc is in switzerland this is a remote control room i ll post any interesting updates as comments to this article they won t come up in rss feeds here are other sources of information all more direct than this blog i mostly try to avoid repeating them cern twitter from the lhc control room atlas control room blog cms e commentary lhc page 1 live update of machine status when i last looked the energy was 3 5 tev and the beam intensities were 1 5e10 higher than the past few weeks the red and blue lines are intensities of the clockwise and counter clockwise beams versus time cms data aquisition live update of cms data collection the main plot is data accumulated versus time it s a constant slope for cosmic rays no lhc beam but could jump up if we get a lot of events from the beams cms event display pictures of the events as we see them in three projections face on side view and 3d yellow lines are particle trajectories red and blue bars are calorimeter energy deposits if a yellow line goes beyond the calorimeters it s a muon right now i think it s re playing events from the low energy collisions of 2009 that will change sometime tonight in my timezone the sun is setting happy passover tags lhc physics posted in basic grad student guests 7 comments particle body count 2 december 18 2009 by jim pivarski as a result of today s talks here s the updated body count all four experiments with a lot of overlap particle original discovery method of observation in the lhc experiments electron positron 1896 e 1932 e peak at 1 0 in calorimeter energy to track momentum ratio also observed in pairs from photon conversions in matter x γ x e e where x is a nucleus photon 1900 planck s quanta photon conversions and π 0 γγ proton 1911 energy loss charged particle s trajectory de dx deuteron 1931 also seen in de dx muon 1936 specialized muon detectors pion 1950 π 0 neutral pion in π 0 γγ charged pions in de dx eta meson 1961 η γγ kaon 1947 k s neutral kaon in k s π π charged kaons k and k in de dx and ring imaging cerenkov detectors phi meson 1962 φ k k lambda 1947 λ 0 λ 0 π p λ 0 π p xi baryon 1964 ξ π λ 0 dark matter wimps not yet two candidates in the unblinded signal region of the cryogenic dark matter search cdms not an lhc experiment the last entry is for yesterday s cdms paper which shows two candidate events surviving all analysis cuts set prior to looking at the result unblinding the probability for background fluctuating up to account for these two events is 20 23 so no one is calling it a signal both are close to the edges of the analysis cuts so even if the observed events had significantly exceeded the background estimates there would be room for doubt this may be the tip of the iceberg for direct dark matter detection but then again it may not posted in guests high school 9 comments the particle body count december 16 2009 by jim pivarski earlier today the lhc finished its 2009 run they did everything they said they were going to do provide physics quality 900 gev collisions and break the world record by colliding protons with a combined energy of 2 36 tev that happened monday as well as many other studies to make sure that everything will work for 7 tev collisions next year we ve been busily finding the familiar particles of the standard model i wrote two weeks ago about the re discovery of the π 0 since then new particles been dropping in almost daily i ll explain some of the already public results below the cut but first i want to point out that there will be another lhc report this friday at 12 15 european central time 6 15 am eastern u s 3 15 am pacific on cern s webcast site this is where all of the lhc experiments will present their results and probably make a few more public also in case you haven t heard there have been a lot of rumors that the cryogenic dark matter search cdms has discovered something interesting they ll be presenting whatever it is tomorrow with a paper on the arxiv a fermilab presentation at 4 00 pm central u s webcast here and a slac presentation at the same time 2 00 pm pacific webcast here it might be the direct detection of dark matter particles which would be incredibly exciting read the rest of this entry posted in guests high school 18 comments erratum no high energy collisions yet december 2 2009 by jim pivarski yesterday when i said the lhc has officially become the world s highest energy collider by colliding protons at 2 36 tev above the fermilab tevatron s record of 1 96 tev i misunderstood a point in the press release that wasn t heavily stressed the lhc has become the world s highest energy accelerator reaching counter rotating energies of 1 18 tev each but the beams were not collided at this high energy yet last week they were collided at low energy and this week they have been accelerated to high energy but not collided the two beams passed by each other in the interaction region held apart by electric fields a few protons on the fuzzy outer edge of the distribution might have collided but the big collisions are yet to come small steps yet very fast from one step to the next posted in uncategorized 2 comments rediscovering the standard model december 1 2009 by jim pivarski in the past week three milestones have been passed the first π 0 particles have been reconstructed from their decay products shown at the public lhc week 1 conference by cms and lhcb the lhc has officially become the world s highest energy collider by colliding protons at 2 36 tev above the fermilab tevatron s record of 1 96 tev the first paper based on lhc data has been submitted to the arxiv by alice the π 0 observation represents the first step in rediscovering the standard model as part of the detector commissioning it s like a walk through history where this step is at about 1950 when the π 0 was first discovered in cyclotrons and cosmic rays the above plot shows invariant mass distributions of pairs of photons observed in cms and lhcb from every pair of photons you assume that they came from the decay of a particle and plot what the mass of that particle must have been for many pairs the assumption is false so you get a combinatoric background of random photons but for photons that actually came from π 0 γγ you get a peak at the π 0 mass the combined distribution is a peak on a smooth background most particles in the standard model are known only through their decay products and this is the first example to be seen at the lhc since we already know a lot about π 0 s we now use them to calibrate the photon detectors needless to say these algorithms are not just being developed now they ve been in the works for years that explains how alice was able to put together and internally approve a paper based on the first collisions in one week for a brand new analysis that would take many months at least posted in uncategorized 6 comments protons have collided in the lhc november 23 2009 by jim pivarski at least it looks like it from this cms event display see the cms e commentary for hourly updates and more information that s how i know which results are public the yellow boxes are silicon strips that detected the passage of particles most likely pions in this case and the green lines radiating from the center are tracks reconstructed from those hits they re not constrained to meet at the center that s an indication that these particles actually originated where the beams collide beyond that the red and blue bars show how much energy was collected in the electromagnetic calorimeter electrons photons and hadrons and the hadronic calorimeter hadrons only respectively no activity can be seen in the muon detector red boxes this is all consistent with what one should expect from the collision of two protons a strong qcd interaction between the quarks and gluons producing a handful of strongly interacting hadrons rather than photons electrons muons or taus which are insensitive to the strong force an electroweak interaction between the quarks and gluons producing possible higgs bosons or any of a number of other exciting possibilities are more rare and will require collecting and sifting through huge numbers of collisions the cern twitter site says that all four experiments saw collision like events it s finally happening tags cms lhc physics posted in uncategorized 4 comments protons have orbited the lhc november 20 2009 by jim pivarski the beam went three times around the lhc ring see cms s e commentary and cern s twitter this is the milestone that was a big media event last year september 10 2008 update now it s 500 times around the ring about 0 05 seconds last year s record was about 9 minutes of continuous beam update up to 9 seconds 30 seconds 50k events seen by cms update and now a beam in the other direction has made a full orbit all you gotta do is smack em together update nov 21 on saturday we got hours of stable beam single beams not colliding this has never been done before with the lhc from here on it s all new territory now i ve got to get to work on the offline data which should be great for detector alignment posted in uncategorized 4 comments beam splashes to arrive at cms soon possibly this weekend november 7 2009 by jim pivarski see cms e commentary for live updates beam splashes are when a beam is threaded part way through the lhc ring then deliberately collided with an absorbing block of tungsten to stop it upstream of a detector many particles are created in this collision most of them are absorbed with the exception of the muons and neutrinos cms can detect muons and what it sees is a huge splash of activity shown in this event display from september 2008 the blue bars indicate huge deposits of energy in the calorimeters they seem to project from the center of the detector but this is an artifact of the software which was designed to visualize collisions from the center the calorimeter cells measure energy not direction so when it sees energy coming from a flood of particles arriving from the right it draws them as though they came from the center you can also see little parallel lines surrounding the central burst like a school of fish these are individual muons seen by the barrel muon detectors which do measure direction update here it is the first cms beam splash of 2009 from the e commentary page the little red lines are reconstructed muon tracks blue dots are raw hits and the yellow blue starburst in the center is the calorimeter energy you can tell that the beam is coming from the right hand side of the detector lhc beam 1 the clockwise direction around the ring posted in uncategorized 4 comments older entries greetings this is a blog by three recent and future cornell graduates pages about tips for comments recent posts coffeeshop physics my last lhc status update 7 tev collisions tonight particle body count 2 the particle body count recent comments valiantly245f650684 on what killed madame curie part 1 anonymous on what killed madame curie part 1 alpheus on the axiom of choice is wrong abdalrhmanretz on my last lhc status update anonymous on what killed madame curie part 4 abby on the axiom of choice is wrong anonymous on what killed madame curie part 1 anonymous on the axiom of choice is wrong anonymous on the axiom of choice is wrong anonymous on what killed madame curie part 1 categories basic grad student greg guests high school jim matt uncategorized undergraduate archives archives select month august 2011 september 2010 march 2010 december 2009 november 2009 october 2009 september 2009 june 2009 may 2009 april 2009 february 2009 december 2008 october 2008 september 2008 august 2008 may 2008 april 2008 march 2008 february 2008 january 2008 december 2007 october 2007 september 2007 august 2007 july 2007 june 2007 blogroll arcadian functor ars mathematica 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