We're physicists searching for new particles, and we're together in Chicago for the 38th International Conference on High Energy Physics. AUA!

Any news on the 750 GeV bump from last year?

VM: The updated results will be unveiled tomorrow morning, stay tuned to #ichep2016 for the latest updates!!! We are working on analyzing the large dataset delivered by the LHC this year, there are also more results to come, stay tuned for updates!!!

Recap of all new results from the LHC will also be presented at the conference on Monday morning at 11:15 US Central time. That session will be webcast live for the public - follow @pressICHEP on Twitter for the URL. Warning: It's a physics presentation for physicists, so expect technical language!

Hey all,

What, in your opinion, would be the single greatest discovery in particle physics today? If there were one thing that you could prove without a doubt based upon your research, what one thing would that be?

Thanks!

DS: Several exciting things come to mind. I'll pick one. Detecting dark matter, or perhaps even opening the door on a whole 'dark sector' of matter would be (will be ;) a fantastic discovery. There are many ways one can go after this question, such as detecting directly the dark matter the Earth is now coasting through, producing dark sector particles in experiments like the LHC, or indirectly detecting their influence through things like neutrino oscillations.

To cheat and name a second - another huge question today is about what exactly is the dark energy.

HL: I second this answer.

VM: Me too!!!

Nobody would choose detection of a graviton or tachyon particle? Not saying either is likely, but where's the fun in that?

HL: Tachyons would be pretty cool.

Hello guys, this is from my girlfriend who's doing her PhD in HEP.

"What kind of limits are we to expect on the SUSY front?"

Thanks!

VM: The first results are being unveiled this morning, check out the Beyond the Standard Model sessions today! We have a large increase in sensitivity with the large dataset we have accumulated at the LHC at 13 TeV!!! The latest updated results have limits on gluinos at around 1.8 TeV. The results for squarks are similar, though for stops specifically, the latest results are around 0.9 TeV.

Will physicists eventually hit a barrier where they are unable to make new discoveries because the tools they would need to are physically impossible to create?

HL: This is a great question. I think the answer is yes and no. The problem lies at the scales we are trying to probe. We have amazing accelerators like the ones at Fermilab and CERN that can generate extremely high energy particles, but we'll probably never create an accelerator that can go up to EeV energies (10^18), and we've measured cosmic rays at those energies. Beyond that, there's the Planck scale where we think quantum gravity becomes important (10²⁸⁾ which is even further. So we'll never build tools to directly probe that.

However, we can try to be smart - so there are lots of ways that physics at those scales do affect things at the scales we can reach. These are sometimes called "indirect" measurements, where understanding something at a scale we can reach actually tells you something very important about something we can't. And I think physics is a history of going back and forth between these direct probes and indirect probes.

So the optimistic answer is that when a hard barrier appears in one particular area, there will always be side channels that we can go down that still provide access to the other side.

Why are you searching for new particles in Chicago? They only have the old kind.

VM: We are in Chicago for the largest particle physics conference of the year. We search for new particles from all over the world! You can also contribute to the effort from your computer http://lhcathome.web.cern.ch/

What's all the cool stuff in the background in your pictures?

HL: the stuff behind me is part of a liquid argon test stand that we use to understand how liquid argon responds to various particle interactions. Liquid argon is a great detection medium - when particles interact in the argon, it emits flashes of light and electrons which can be collected to understand what the particle was and how much energy it has. However, argon is a liquid only at low temperatures, 85 K or -190 C, so you need to have a lot of infrastructure to handle that. What you see behind me are a vacuum cryostat for insulation (like a giant thermos), vacuum pumps, a cryocooler to get the temperature down, a gas handling system to move the argon around, etc.

DS: I'm just in my office at the university. The clutter of equations and sketches on the board is from research that some undergraduate students have been working on over the summer. The formulas describe neutrino oscillations and the detailed sketches are from a new detector design a student is working on.

VM: I'm at Fermilab at the Remote Operations Center, which is essentially a satellite control room that is connected to the other control rooms at CERN. From here, LHC scientists can take shifts to run the experiments and participate in the data taking activities. The screens show some of the displays we look at when we are taking shifts.

Which experiments have satellite control rooms at Fermilab? I thought the CMS one in building 6 of the Meyrin site was a bit over the top...

DS: There is a CMS remote control room at Fermilab. I'm not in the group, but there are something like 100 Fermilab scientists and engineers working on the LHC and CMS, so there is a ton of activity at Fermilab related to LHC science.

Across the atrium from the ROC at Fermilab is ROC West, the Remote Operations Center for all the Intensity Frontier experiments happening at Fermilab, including many neutrino experiments like MicroBooNE, NOvA, MINERvA, MINOS, etc. This is a new facility at Fermilab and it's really cool to have all the experiments controlled from a single location. Great for communication between groups and really great for visitors!

Here's a pic of the room, though these days it would typically have many more people running around: http://communication.fnal.gov/asset/detail?recid=1827810

In your opinion, are ongoing experiments now relegated to exploring parameter space until we get bigger and better colliders or is there a possibility of observing new BSM physics in any ongoing experiment today?

Do the amount of papers published on the 750 GeV diphoton excess perhaps indicate that theoretical physics is entering a bit of a drought now?

HL: Tough question. My personal opinion is that ongoing experiments are not relegated to exploring parameter space and that we can observe new BSM physics. The current run of the LHC is obviously a big step, and I think no one would be surprised if something popped out in the next year or two. If that doesn't happen in the next year or two, then probably the chances the LHC makes another big discovery like the Higgs go way down (Verena might have an opinion on that).

But dark matter experiments could see stuff any day. Understanding neutrino mass is BSM. Muon g-2 is trying ot understand an anomaly that points to BSM. Electric dipole moment experiments could come up with something. And of course dark energy. That's just to name a few that pop to mind. There's a lot going on that we can't explain and any one of these efforts could find something cool.

That said, it's definitely true that we aren't discovering new models and advancing new theories every few years like it seemed was going on 30-40 years ago. From that point of view, I guess you could characterize what's happening as a drought, but probably I would argue that it was just particularly wet when all these theories were being put in place...(glass half full)

VM: We have to look for new physics in all possible places that we can!!! There are still lots of unexplored regions, especially with the quickly growing dataset at the LHC, so stay tuned. About the question on the theorists, I think that it is extremely positive that our theory colleagues are actively working with us to interpret the data!

Hey, recent Physics graduate here, I did my dissertation and masters project in Extra dimensions and the AdS/CFT respectively.

Do you think it will be possible to begin to test elements of such theories at the LHC in the coming years (via microscopic black hole or graviton production for example), or are the energy scales too great?

VM: We are actively looking for models with low scale gravity. Some results will be presented this year in ICHEP. So far, all results are consistent with expectation, but stay tuned because we are getting a lot of data and there are many more analyses to come.

According to you, how close are we to finding evidence of the dark matter?

HL: I would say we already have extremely strong evidence for dark matter from astrophysical observations. We see the effect of dark matter on galaxies, clusters of galaxies, gravitational lensing, the cosmic microwave background - all these measurements at widely different scales point to there being missing matter in our universe that we think is dark matter.

That said, we don't have strong evidence for dark matter particles, which is more what I'm looking for. And there, probably my answer depends on when you ask me. I'm in a pretty good mood today, so I think we're pretty close, but you never know.

Thanks for this answer. I was actually thinking of dark matter particles -- I mean, really detecting the real thing :-)

So pretty close would mean weeks, months or years? ;-)

Years before we're sure. We just had a dark matter specific conference last week where some recent results were presented (see LUX and PandaX if you're interested), but they didn't see evidence for particles. We have one big experiment coming online now (XENON1T), and several more on the way over the next five years. IF we don't see anything in the next 5-10 years though, I think it's back to the drawing board.

That said, there is one experiment that's claimed a signal for years (DAMA) - no one else has been able to confirm that result so it's not widely accepted, but no one else has been able to explain it either, so you never know. Efforts are ongoing to confirm it or rule it out.

Short answer though is years.

Where do you guys get your physics acronyms from?

HL: Via a long tortuous process involving committees and the ballot box. I would say more than half the time, we start with something we want and then force the words to fit. Two of my favorite examples of this:

PICASSO - Project In CAnada to Search for Supersymmetric Objects ZEPLIN - ZonEd Proportional scintillation in LIquid Noble gases

So.... Diphoton?

VM: The updated results will be presented tomorrow morning at the conference! There will also be a live webcast session on Monday that should include an updated on the results. This will happen 11:15 - 12:10 Central time. We will post the webcast link on twitter, follow #ichep2016

Thanks for doing this!

What is the LHC like to be around? Is there a sound it makes? Does the knowledge of how crazy stuff is in there feel weird when right next to it? Is there any other machinery and tech you use that you think is as cool?

DS: I've visited CERN and the LHC many times, and it is indeed inspiring. I don't work on the experiments, but did get a tour of the ATLAS detector once during a shutdown. It was amazing to walk around the detector like it was a building, up and down stairwells that connect different parts of a single particle physics detector!

In my research we study neutrinos which also involves some amazing detectors and technologies. Some neutrino detectors are even bigger than the LHC experiments, like this one (Super Kamiokande) in Japan: https://www.google.com/search?q=super+kamiokande&espv=2&biw=1406&bih=782&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwibn-jjnKjOAhUFYyYKHbrODzEQsAQINA

or this one (NOvA) in Minnesota that detects neutrinos produced at Fermilab and sent through the Earth for 800 kilometers to the experiment! https://www.youtube.com/watch?v=gFpK00WJl90

or this enormous neutrino telescope at the South Pole called IceCube! https://www.google.com/search?q=icecube+neutrinos&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjJ7rqOnqjOAhXDJCYKHaqBA4sQ_AUICCgB&biw=1406&bih=782

There are a wide range of technologies that have been developed to study neutrinos at energies that range over a dozen orders of magnitude from low-energy solar neutrinos, to medium energy neutrinos produces with accelerators, to ultra-high-energy neutrinos generated in the galaxy or beyond!

VM: This is a very interesting question, there are several people who have looked into the sounds of the LHC. For example here is an artist's interpretation of the LHC sounds http://arts.cern/bill-fontana You can also find a sonification of the LHC data as it arrives http://quantizer.media.mit.edu/

What gets you up in the morning?

DS: My two year old daughter! Haven't needed an alarm clock since May 2014.

VM: SCIENCE!!!!!!!! Well, also coffee, a cold shower....

HL: At least two hits of the snooze button, before my dogs get annoyed and start barking to go outside.

Haven't all three neutrinos already been discovered/measured? Is there evidence there are others out there?

DS: Great question! Indeed we know for sure there are three "flavors" of neutrinos: the electron, muon, and tau type neutrinos. We study these in detail in all kinds of experiments. Turns out there are indeed hints coming from some experiments that there may be additional types out there as well! But these are even more challenging to explore experimentally because these new neutrinos would not interact via the so-called weak nuclear force like the standard neutrinos do. If these exist, therefore, we refer to them as 'sterile' neutrinos, and we look for evidence of them through their influence on the standard neutrinos - specifically by inducing a new kind of neutrino oscillation. There are many experiments out there looking for exactly such signals. If we find clear evidence for sterile neutrinos, it will be an extremely exciting discovery!

Hey guys just wanted to say you guys are ridiculously smart and awesome people for doing this.

What physics book would you recommend for me to read to learn more and just find out about interesting things in physics?

DS: Hi! If you're looking for a general audience book I recently read John Gribbin's "The Universe: A Biography" - caught my eye at an airport. It's great for the emphasis on the connection between particle physics and cosmology - connecting all we've learned about the physics at sub-atomic scales with the history of the entire universe. Pretty cool.

Thank you so much! Will definitely check it out, that's the exact type of book I was looking for!

enjoy!

Hi,

I've always been interested in particle physics. Where, in general, do you believe the field is going today, after the discovery of the Higgs Boson? What do you think about the ILC? And finally, is there any time I could visit you to have a discussion on particle physics (I'm in Wi).

Thanks

Hi Wisconsinite! If you're within driving distance of Chicago, there are a few public science events going on this week in conjunction with the conference - lots of particle physics to talk about. There's a physics slam at the Sheraton at 3 p.m. on Sunday, and a public lecture on gravitational waves on Tuesday, Aug. 9 at 6:30. There's also Fermilab 40 miles west of Chicago - the biggest particle physics lab in the US. They have ask-a-scientist events, etc. Here's their tour/event schedule: http://ed.fnal.gov//home/visitors.shtml

VM: The ILC is an interesting proposal that would be complementary to the efforts at the LHC. Right now, many of my colleagues are actively researching on how this new experiment could be built, what kind of new particle detectors we would need, and what kind of new exciting physics could be done with it.

Hi guys!

I'm about to go into my masters for Particle physics, have no relevent work experience outside of my degree and am average when it comes to ability as far as physics uni master students seem to go.

I'd absolutely LOVE to go into a PhD for this field but worry I lack the ability? I've never had such a passion for anything but it doesn't seem to come to me as easily as top students so I worry my interest won't be enough.

Any advice or stories?

DS: Don't underestimate the importance of your passion for the subject! There are many ways that people contribute to advancing science, from deep thinking theorists, to instrument designers and builders, to data analyzers. Look for the scientific questions that excite you and then the ways to contribute that match your interests and experience - it's probably there.

You guys sound like you like to party. Where are you going tonight? And what are you drinking?

VM: We will be in the biggest particle physics conference of the year!!! Probably drinking coffee. It was once said that a scientist is a machine that transforms coffee into new theories.

HL: Also the hotel bar is pretty expensive. I'll probably get at least one beer at Rossi's before the conference is over. But I'm not drinking Malort.

Well, if you need some recommendations let me know. I live downtown and know of a couple of affordable watering holes.

And you should definitely try malort. Or get some of your colleagues to do it while unobtrusively filming them on your phone.

HL: I live in the city too - I once convinced about 8-9 colleagues in town for a collaboration meeting to drink Malort at the J&M tap on Augusta and Leavitt, and I was promptly kicked out of the collaboration...

Is "Particle Man" by the Might Be Giants your official theme song? https://www.youtube.com/watch?v=sNT8SMlqLJA

DS: Doing the things a particle can!!

HL: For whatever reason, when Dave and I used to do presentations on Force and Motion for CPS kids, we always listened to the Gin Blossoms.

What are the chances of dark-matter being discovered within this decade?

HL: What's your prior? I don't think we have any way of putting a real probability on this, so any answer I give is a complete guess based on nothing but my gut, meaning it's not at all indicative of the state of the science but much more indicative of my state of mind.

25%? (I actually think that is pretty high)

For a slightly more technical answer, this next decade will answer whether the dark matter particles couple to the Higgs at O(10%), and many of our leading theories would predict such a coupling.

How come the parallel sessions aren't being broadcast on a webcast/over vidyo? - I've seen that the plenary session on Monday is going to be broadcast, but it feels like I'm missing out a lot from not being able to attend the parallels, the analysis I work on is being presented in half an hour after all!

VM: Unfortunately, this is common in big conferences. There are too many sessions happening at the same time and it would be complicated to broadcast them all. You can catch a live webcast of the opening plenary session on Monday. Follow @pressICHEP on Twitter for the URL

All four ATLAS, CMS papers from 2012 and 2015 have apparently seen some excess in the Z-gamma (decaying to lepton pair and photon) at mass 350-380 GeV.

Now, it seems that 12.9/fb of the 2016 CMS data have an excess in that range, too. Is ATLAS seeing some local resonance in the Z-gamma near the mass 350-380 GeV, too?

VM: ATLAS is going to present the status of the Z-gamma resonance search tomorrow 17:50 - 18:10, if you can access the conference agenda page you will be able to see the slides at http://indico.cern.ch/event/432527/contributions/1071847/ Also stay tuned to the ATLAS public results pages, updated conference reports will be posted there!

For your reading pleasure, here is the ATLAS public results webpage: https://twiki.cern.ch/twiki/bin/view/AtlasPublic And the CMS public results page: http://cms-results.web.cern.ch/cms-results/public-results/publications/

I've been reading that the diphoton bump found in December is likely to be a statistical fluke after all. What if anything did we learn from this?

We'll know more about the diphoton results tomorrow morning. But if you want to brush up on how we get to discovery in particle physics and how statistics fit in, here is a nice article CERN recently published: From CERN: http://press.cern/backgrounders/12-steps-idea-discovery

VM: The updated results from both ATLAS and CMS will be presented tomorrow morning at the conference. Stay tuned to #ichep2016 for the latest updates! There will also be a live webcast on Monday that should include a summary of the results. We will post the link on twitter follow #ichep2016

The Standard Model tells us the elementary particles that constitute all matter, but we are constantly finding new particles that are "combinations" of these more elementary particles. What new and fundamental things can we learn from the discovery of those composite particles? Or there's no more to do besides putting them into a catalogue?

VM: Absolutely not! It is as important to understand how new particles interact among themselves as discovering new particles. Discovering new composite particles and measuring their properties gives us valuable information to understand their interactions.

Hey guys, do you get invited to enough parties to not hate the infinite improbability drive?

On a serious note, can you think of any modern science fiction that accurately depicts your work?

You might even know one of my friends who i think is working for your team, an Indian guy named Ritoban

HL: I love Rito! I also love the infinite improbability drive, it's one of my favorite parts of those books.

On the serious question, nothing comes to mind. But I'll be honest, I read a lot more fantasy than science fiction.

You are probably sick of these questions but what are the possible practical applications of your research? Even if its science fiction?

HL: This is another complicated question for me. Lots of practical applications have come out of physics research, but they weren't really the point of the original research. So in my case, dark matter, sort of by definition, dark matter doesn't interact much. So I'm extremely uncomfortable talking about the practical outcome of discovering dark matter particles. What excites me is that it's a missing part of our understanding of the universe and I want to complete that picture.

That said, the techniques we develop, namely low energy radiation detectors with particle identification capability, turn out to be well suited to detecting nuclear material. So there is a lively cross-program with nuclear non-proliferation activity. So that's one.

I don't know if you guys deal with this but what are your thoughts on the erhic upgrade that they want to perform on the rhic at brookhaven labs?

VM: This is not the area of expertise of any of us here, but the e-rhic project is an exciting new idea that will teach us a lot about the structure of the nucleus. A lot of my colleagues are working to make it a reality.

HL: Just to add a little context, I literally just had to google "eRHIC" to remind myself what it is, so I'm definitely not qualified to answer right now.

Hi! Thanks for doing this.

So, if I understand Hawking radiation correctly (and I almost certainly don't), Heisenberg permits spontaneous pair production to happen near the event horizon of a black hole as long as it's for a short enough period of time. One particle is captured by the singularity and one is emitted. Heisenberg is only satisfied, though, if the captured particle is quickly annihilated. What is the mechanism whereby the particle gets absorbed by the singularity while maintaining all the conservation rules?

Thanks!

HL: wadeguthrie, I'm going to be completely honest and say I probably know less than you do. If I had to guess, though, I would say that Heisenberg is fine as long as there was enough energy to begin with. You can create the particles and reduce the total amount of energy available in the local area. If those particles don't re-annihilate, then the energy is just less. This is why it's an energy loss mechanism for the black holes themselves. Somewhere, Stephen Hawking is cringing.

What do you think, in terms of hardware and laboratories, we need to make further advances in quantum physics (like a new way to see events or a bigger collider)? Also, what do you think will be the next big discovery of particle physics?

Keep the research going, physicists are the real heros of this world!

VM: Research on better detectors and accelerators is an active field. Many new results are being presented at ICHEP. For accelerator-based experiments like the ones at the LHC, the current challenge is to design detectors that work in a collider where many collisions happen at the same time and where hundreds of particles reach the experiment simultaneously.

Hi. Is it possible for there to be another big bang at any instant anywhere in the cosmos? I've wondered why the first happened, and what prevents another from happening.

HL: I just had to ask the group "We don't think there will be another big bang anywhere, right?" So take this answer with a grain of salt, but I don't think we know why the first one happened except that it probably can't happen anymore because everything is spread out. The conditions for the big bang are beyond anything I can understand, but when you consider that the entire energy and matter content of the universe was at a single point at the big bang, but is now spread over how ever many billions of light years, you can imagine that the conditions required for the big bang are no longer satisfied.

Do you think we would know what "the entire energy and matter content of the universe at a single point" would look like from a distance... I mean... I can't really wrap my head around the idea of space being collapsed into a point...but... I feel like we may not be able to see another one of those points near us if there was one. I am just thinking if I wanted to develop a neurosis, I feel like this one would be just as justified of one as any other.

HL: Do you want me to feed the neurosis or dispel it? I'm pretty sure if the entire energy and matter content were located at a single point nearby, we'd know about it and wouldn't really have time to develop the neurosis. I would say don't worry about it.

There's always the heat death of the sun! Or the accelerating expansion of the universe that will eventually leave us alone and lost with no stars in sight!

Are you guys currently working on anything that could possibly lead to a new discovery?

VM: Our experiments are designed to try to discover something new! We also pursue as many different angles as possible, looking at information from colliders on earth or from outer space.

Cool. My sister works at fermilab. She just got her phd in electrical engineering.

What is the social aspect of your work like? What's the atmosphere like? Can you tell us some stories about the kind of people you meet in this line of work?

VM: I think the most striking thing is that in this line of work you meet people from all over the world! It is a very collaborative environment and in any given day you can easily interact with people from 10 or 20 different nationalities.

Which parallel session do you recommend?

HL: Definitely Heavy Ions: Collective Effects and Correlations.

HL: My talk is Saturday morning in the Detector R&D one. That's probably a better answer.

My Experimental Physics lecturer, Dr. Karl Jakobs would apparently be leading the ATLAS experiment starting from March 2017. Would Prof. Verena Martinez Outschoorn please say hi to him in the event that she does meet him and say that our class in Freiburg really did enjoy his lectures? :P

VM: yes, he will be our next spokesperson!!! It is wonderful that you enjoyed the lectures, thanks for posting!

Greetings from a b-quark phenomenologist. When can we expect the B->K^*mumu results from ATLAS?

VM: I'm afraid I don't know off the top of my head, but please follow the ATLAS page that lists the latest results here: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/BPhysPublicResults

What's bigger, a molecule or particle?

A molecule by a surprisingly big margin, actually. The nucleus of an atom is about 100,000 times smaller than the atom as a whole - a nucleus is super compact. Picture a tennis ball sitting at the 50 yard line in a football stadium. Inside of that nucleus are protons and neutrons and inside of those are quarks - which we believe to be fundamental particles. Going the other way, molecules are made up of multiple atoms, so many many times bigger than the fundamental particles deep down inside them!

A dark matter related question: We have strong evidence of gravitational effects on galaxies and galaxies clusters that must be caused by amounts of masses we can't detect in the EM spectre. We can actually detect the space-time curvature, thus implying "dark matter".

But could this space-time curvature be caused by something else entirely, so that no real mass is there? Maybe the curvature is just the lowest energy state possible in those regions of space?

Thanks

HL: People do think about alternative theories that can explain the evidence for dark matter without needing dark matter. A prominent one is Modified Newtonian Gravity or MOND. This was originally just a small change to Newtonian dynamics to explain galaxy rotation curves, but there is now a fully relativistic treatment. The consensus in the field however is that it takes a lot of tweaking to get MOND to agree with all the data, and it can't explain everything, whereas it's much simpler to get things to work with dark matter particles.

Always be wary of conventional wisdom, but

is there any books that discus the detector details?

VM: There are a lot of details and references in the review sections of the "particle data group" publications: http://pdg.lbl.gov/

HL: Hi all, I've had a great time, thanks for all the questions. I have to eat some lunch now otherwise I'll be really cranky for the afternoon sessions at the conference. See you guys all out in Chicago!

Is there any way to get into the field without going to school? I am a 30 year old man, never went to college, and I have a well paying job already, but I am looking to enter a more intellectually stimulating field.

I have learned various drawing and modeling programs over the years, I know a decent amount of math and can speak 3 languages so far. I can handle any kind of data entry and am generally a faster learner than everyone else.

VM: Particle physics really requires going to school and getting a PhD in this field. But nothing prevents you from starting now. You would not be the first and certainly not the last to enter this field at your age. There is an example of a mechanic who became a physicist in his 30s, check this page out http://news.ufl.edu/archive/2015/03/shifting-gears.php There are also opportunities to work with science that don't require a science degree, such as mechanical or electrical technician, or a science writer.

Opinions on Dr. Emlyn Hughes? - Columbia University student who took his Frontiers of Science class

VM: None of us have worked with him directly. He is actively working on ATLAS.

Hi, thanks for doing this, I am a recent Physics (BSc) graduate starting PhD in Theoretical HEP next month. I would like to ask what is your take on the semi-recent D0 X(5568) particle? I have read articles about it being a cone-cut anomaly as well as being consistent with the properties of a tetraquark and I am interested in your take on the data.

VM: This is an interesting topic. The LHCb experiment at the LHC searched for the same particle in two channels and did not find evidence for it. There is an update of this result from D0 at ICHEP and they have released a new preliminary result searching for this mysterious state in the semi-leptonic decay channel ( http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/B/B67/B67.pdf ). More results will certainly come in the future from these and other experiments.

Hi there, Second year bachelor student here! (3.rd semester starts in a month)

What in your opinion mattes most when getting accepted into ph.d programmes? Is it recommendations or grades?

VM: Both are important. Keep up with the good work and do your best. Good luck in your applications!

HL: For a little more detail, I think at most places there's sort of a minimum grade requirement and if you clear that bar, then it's the recommendations that matter more.

I read a book about how everything we do is orchestrated on subatomic-particle-level, so essentially there is no free will. Can your experiments or your opinion share some light on that concept (in case you have heard of this)?

HL: I haven't directly heard of this particular theory, but there are two reasons in my mind why "free will" does exist (speaking for myself only).

One is a the subatomic particle level, things are not deterministic. Quantum mechanics relies on probabilities so for a given initial condition, there can be many outcomes. In other words, we are in the opposite condition from where things would be "orchestrated."

Two, even if things were more or less determined at the subatomic level, by the time all those little subatomic interactions added up to form human decision making, the system is so complex that I don't think strict determinism could apply. I guess I'm pulling in chaos theory here, but there are so many components, that again, from a single initial condition, there would be many outcomes.

So I believe free will is completely consistent with my understanding of physics.

DS: Thanks everyone for all your awesome questions! Time for us to sign off here and get back to all the presentations and discussions here at #ICHEP2016. -Dave

What are the experiments good for?

This isn't meant to be a troll question but I'm a very practical kind of guy. What is the possible application of the science learned through the experiments? Is it even possible to use most of the knowledge or is it kinda "we just don't have the technology in order to make an actual use of this data besides simply researching what happens"?

HL: I answered a related question above, I'll expand a tiny bit more here, otherwise it's a copy and paste.

This is a complicated question for me. Lots of practical applications have come out of physics research (nuclear weapons being an obvious one, but anytime you get an x-ray or a pet scan, or actually, use the internet, since the WWW was invented at CERN), but they weren't really the point of the original research. So in my case, dark matter, sort of by definition, dark matter doesn't interact much. So I'm extremely uncomfortable talking about the practical outcome of discovering dark matter particles. What excites me is that it's a missing part of our understanding of the universe and I want to complete that picture. Most of our research is really aimed at this "basic science" question, which is understanding how our universe works, and is not "applied."

That said, in my case, the techniques we develop for dark matter detection, namely low energy radiation detectors with particle identification capability, turn out to be well suited to detecting nuclear materials. So there is a lively cross-program with nuclear non-proliferation activity. So that's one that is directly related to what I do.

Someone crosspost to /r/AskScience yet?

We submitted a crosspost to /r/science but not /r/askscience

I've become increasingly interested in physics and might major in it, so I was wondering if you could describe to me your average day... How is the workload? Stress?

VM: One of the cool things about being a scientist is that days can be quite varied. Sometimes we are getting experiments to work, other days we are programming and analyzing the data we have taken. We also travel and discuss our results with other physicists at conferences such as ICHEP! The workload varies, this is definitely not a 9-5 job. When we are taking lots of data and trying to produce results we can work more intensely, but then there are periods when we can have a more relaxed lifestyle.

Who are the top professors working on the LHC?

VM: The LHC is a collaborative project. There are no top professors, everyone’s work is important. There are more than 10000 physicists, engineers and technicians working on the LHC experiments. The work of all these people is important to do good physics.

HL: Verena Martinez Outschoorn

This is more of a general question for physicists. What was your career path to get you to where you are today? What do you wish you had know/done whilst you were studying to get you there faster/to get further?

DS: My path was fairly 'typical', like Hugh's, since graduate school (after my Ph.D, I was a postdoc at Fermilab before moving to the University of Chicago), but before that mine was quite different. I started out in college studying architecture and did so for three and a half years! My third year I studied abroad in Germany and spent the year obsessed with popular books about physics. Upon my return to the US I took an elective course in modern physics. I approached a professor in the department about research opportunities and, thankfully, he took me on. I switched majors, spent most of my free time in the lab, and during my last year in school got the amazing opportunity to travel with my advisor to the South Pole where his experiment was being done! If I wasn't already, I was definitely hooked on science and particle physics after that - have been chasing neutrinos ever since.

HL: Mine was probably a straightforward career path although I backed into it. Graduated college with a degree in physics, but didn't have plans to go to graduate school. I also didn't have a job, so when my senior thesis advisor was hired at a different university and asked me to work for him for the summer, I took the job. It was great, setting up a lab, buying cool stuff, I had a blast. Meanwhile, I interviewed at companies and stuff, but nothing stuck so when my advisor suggested I apply to grad school (that I really had not thought about), I figured I liked what I was doing and so I applied. I ended up staying for another 6 years before getting my degree.

Then you have to do a postdoc for a few years. Then, if you're lucky, you can catch on as a permanent job. So it's long. I went 10 years from college to having the promise of a long term job, and now I have to go through tenure.

I think that's pretty much teh standard career path, and lots of people drop off along the way for lots of different reasons.

I'm not sure there's anything I could have done to get faster or further. Physics experiments have long time horizons and because of funding and sometimes unrealistic projections (by physicists), you should never believe a physicist when they tell you how long something will take without doing your own checking (teh experiment I was supposed to write my PhD thesis on is only starting to take data now). But things have gone well for me. We could talk about this topic a lot.

Will you guys change the name of dark matter after you find it?

HL: Hopefully one of hte many names we have for dark matter candidates takes over (WIMPs, axions, Kaluza-Klein particles...)

Hi,

recently I watched Particle Fever and was quite impressed that one can break down the state of current research at LHC to a competition between the "multiverse" theory and supersymmetry.

The movie ends by stating that the competition hasn't been settled yet and both world-views remain competing. Is there an update on this? Can you recommend a paper/resource that explains this competition in more detail as a follow-up on the movie?

Thanks and kind regards from Germany.

VM: Thank you for your message from Germany! Supersymmetry and multiverse are only two of the many possible new physics models we explore. The “competition” in the movie takes a bit of artistic liberties, we do not really view this in such terms. So far, all results in the LHC are consistent with the expectation, but we continue to search for new physics with the new data collected, so stay tuned!!!

How well do the collisions at the LHC relate to what we would observe in our universe, that is, where would these collisions occur naturally?

Secondly, let's say we were looking at a particularly violent part of a galaxy, such as the center. Could there be processes happening there that would contribute to the disparity between theory and what we observe, meaning could it be a possible source of dark matter/energy? Specifically, I'm thinking about a gamma ray burst and its interaction with the space and the particles that reside in the path. Laser wakefield acceleration is extremely interesting to me and what I have spent my years researching as an undergraduate. The relativistic energies we can accelerate electrons to in a matter of centimeters using a high power laser is, to me, astonishing, so I'm extremely interested in the effects that such a powerful phenomenon like a GRB has on space and time.

Thank you, wish I had time to ask more.

DS: One of the cool things about collisions at the LHC is that they reproduce conditions from the very early moments in the universe, tiny fractions of a second after the Big Bang. This is one way we think we know how things evolved in those early moments and beyond to lead to the universe around us. Pretty cool.

It has worked great with the Z-gamma. May I ask for one more URL and scheduling of a talk if there's any? EXO-16-015 is a CMS paper seeing a 3.7-sigma (locally, ideally) excess for a 2.0 TeV excited quark in jet+photon.

Is there a similar talk or paper by ATLAS? Thanks!

VM: This local significance is hard to interpret without calculating the associated global significance. The reduction in significance can be quite large with objects like photons in the final state.

They calculate the global significance to be 2.84 sigma or so. But it's CMS. Is there an ATLAS work on that?

VM: I'm afraid I don't know off the top of my head and it is hard to look up the results while doing the AMA. Please follow the website where the latest results from ATLAS in this area are posted https://twiki.cern.ch/twiki/bin/view/AtlasPublic/ExoticsCONFnotes

Do you think Supersymmetry or some sort of spin 3/2 particle is real? What would the implications of such a discovery be?

VM: Supersymmetry is a well motivated extension of the Standard Model and spin 3/2 particles exist when gravity is included (supergravity). At the LHC we are avidly searching for supersymmetry, you can see lots of new results presented at ICHEP. Only data will tell us if it is real or not. The implications are far fetching since there are many open questions in our field and supersymmetry can be an explanation for some of them.

hi what type of data generated by each collision? and what type of mathematical/physics equations used to analyze it? is there books to expand in this particularly? - i have EE/phsx background-

HL: This is a pretty broad question. Lots of different types of collisions (energy, particle type, interaction type,...), lots of different kinds of signal (light, charge, heat,...), lots of ways of detecting that signal and recording it (analog, digital, analog to digital, timing), and then lots of equations used to expand on it.

My favorite book on particle detection is Glenn Knoll, Radiation Detection and Measurement: https://books.google.com/books?id=4vTJ7UDel5IC

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VM: This is an awesome question, nice! It would be hard to choose. The size is not important, what matters is the energy and luminosity it delivers.

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VM: Well, in this case the integrated luminosity would be 1/4 (4 weeks in a month). So you are asking whether I prefer 1/4 of energy or 1/4 of the integrated luminosity. Both are valuable, for different type of physics. To search for new physics like supersymmetry, an accelerator with 4x more energy would be better.

HL: I think I accidentally deleted this question - it was would we rather have an accelerator around the equator that took data once a month or an accelerator that was a quarter the size once a week. Scaling hte energy and luminosity from the LHC.