1 2012 promises to be a truly historic year for science.

2 Just before Christmas, researchers working at CERN

3 near Geneva, announced that they had caught a tantalising glimpse

4 of the Higgs boson.

5 I'm Jim Al-Khalili and, as a physicist,

6 I must say that following the search

7 for this so-called "God particle" has been incredibly exciting.

8 Sometime this year, researchers hope to be able to declare

9 the Higgs finally, officially discovered.

10 If confirmed, it will be the most important scientific discovery

11 of my lifetime.

12 It'll be evidence for one of the most

13 all-encompassing ideas in physics.

14 That at the heart of everything

15 is the simple and enchanting idea

16 of symmetry.

17 The search for the Higgs takes us deep into the most important

18 questions about how the universe works and how it was created.

19 Horizon has been following the final stages of the hunt

20 for this most important and elusive of particles.

21 This is CERN, headquarters

22 of the European Organisation for Nuclear Research.

23 It's home to some of the thousands of scientists

24 who have been doggedly hunting

25 the elusive Higgs boson

26 and the £6 billion experiment that they're using to do it.

27 Especially built to find the one particle

28 that's thought to give substance to everything in the universe.

29 This is fantastic. Any one of those 40 million collisions

30 happening every second could be giving us a Higgs boson.

31 Could be that one right there.

32 In the autumn of 2011,

33 when Horizon was at CERN,

34 there was already a sense that this near 50-year quest

35 was reaching its final stages.

36 Yeah, I think this is the end. This is the end, one way or another.

37 We're definitely in the end game now.

38 I think that this time next year,

39 it will be there or it won't be.

40 It's a search that's dominated the careers

41 of a generation of physicists.

42 Personally, I got a job saying I wanted to do this in 1993.

43 It's the 11th year now.

44 About ten years, me. Yeah, and about 5 years for me.

45 Since 1989.

46 That's over 20 years.

47 But while there are thousands of scientists in pursuit,

48 only for a few will there be prizes

49 and a place in history.

50 The Higgs is going to win a Nobel Prize,

51 so everybody wants to be a part of it. This is the goal

52 of every physicist. I mean, you won't spend 20 years

53 if you don't believe in something.

54 There's a lot of people who are interested in this, so...

55 So yeah, it tends to get exciting.

56 Not sleeping very much!

57 It's a big collaboration. "What did you do?"

58 Everyone wants an answer to that.

59 INTERVIEWER: And are you two competing or working together?

60 Together. If he finds it, I'll take the credit.

61 Amongst the intrepid Higgs hunters

62 are Jon Butterworth

63 and his colleague Adam Davison, from University College London.

64 They've been drawn here, like all the other scientists,

65 by the potential of the Large Hadron Collider

66 to find the missing boson at last.

67 It's a great opportunity for us to finally understand

68 whether the Higgs exists.

69 Physics won't be the same after this.

70 Even a null result here will re-write the text books.

71 This is it. This is where it's going to happen.

72 The problem with hunting for the Higgs

73 is it can't be detected in everyday conditions.

74 To find it, scientists need to return

75 to those at the very beginning.

76 Well, almost - to the conditions just after the Big Bang.

77 When, the theory goes, the Higgs and everything else

78 was first created.

79 So here we have the Big Bang.

80 Deserves a little bit of colour, I think.

81 BOOMING EXPLOSION

82 And then the timeline of the universe.

83 This is where we are.

84 It's now, the age of the universe,

85 about 13.7 billion years

86 after the Big Bang.

87 So working backwards,

88 we know that a few 100,000 years ago,

89 we had the dinosaurs.

90 So, here's a dinosaur.

91 DINOSAUR ROARS

92 Then life itself, the first DNA,

93 is about 4 billion years ago.

94 Before DNA, there was the Earth.

95 Before that, stars.

96 Before them, atoms.

97 And inside atoms,

98 you have the most fundamental building blocks of existence.

99 The big question is where did those building blocks come from?

100 The answer to all that lies in the first second.

101 In this one crucial second, all the elementary particles were created

102 Including, scientists believe, the Higgs boson.

103 The mysteries of existence lie within this second.

104 Certainly, we understand the science, we understand the physics.

105 Backwards into this second,

106 but at some point we just run out of knowledge.

107 The Large Hadron Collider is allowing us to see

108 right back to 10 to the -12 seconds

109 after the Big Bang.

110 Beyond that, here be dragons. Or dinosaurs!

111 The Large Hadron Collider's technique to transport scientists

112 to the moment just after the Big Bang is as violent

113 as it is ambitious. 100 metres underground, it takes protons

114 from the nuclei of atoms

115 and collides them, at almost the speed of light.

116 These protons are colliding at huge energies,

117 and in those collisions

118 a large number of particles are produced, hundreds, thousands even.

119 And trying to look at those particles that are produced,

120 and understand what happened in those collisions,

121 is what the LHC is all about.

122 Somewhere buried in this wreckage, they hope to unearth the Higgs.

123 It would be proof of the existence of a field

124 that scientists believe surrounds us all the time.

125 And that appeared in that first second of creation.

126 As the heat and fury ebbed out of the Big Bang,

127 so the theory goes, the Higgs field condensed.

128 As particles travel through this field

129 they get slowed down, like travelling through treacle.

130 This is what gives them mass.

131 Without gaining mass, particles

132 would have continued to fly through the universe at the speed of light.

133 Never clumping together to form you, me, blackboards, well, anything.

134 To have deduced the presence of something as weird as the Higgs,

135 just from theory and from other previous data,

136 and then to find it in nature, would be a hugely exciting vindication

137 of our picture of what is going on.

138 Finding something that's all around us is surprisingly tricky.

139 Scientists need to create a disturbance in the Higgs field

140 to detect the boson itself.

141 This is what the LHC is attempting to do, by colliding particles.

142 It's a challenge other particle accelerators

143 have tried and been unable to complete.

144 Because for all scientists sense that the Higgs ought to be there,

145 it has proven spectacularly difficult to find.

146 The idea of the Higgs boson was first proposed in 1964.

147 Which was a very long time ago, before I was even born.

148 Many years of work have been leading up to this point,

149 so it is absolutely exciting to be here

150 at the point where the discovery might happen.

151 What's made all the difference at the LHC

152 are the incredible energy levels the collider can reach.

153 Pushing further back in time into that crucial first second.

154 This has opened up new places to search for the Higgs,

155 a hunt that's defined in terms

156 of what mass the Higgs itself might have,

157 measured in GeV, or giga electron volts.

158 So on this line of what the mass of the Higgs might be,

159 we can draw on what previous experiments have tried,

160 and where they have been able to exclude it from being.

161 After decades of work, the LEP collider at CERN,

162 a predecessor of the LHC,

163 ruled out the Higgs being at the bottom end of potential masses.

164 In fact, they were able to say that the mass of the Higgs is,

165 with 95% confidence, 114 GeV, or more.

166 So after LEP, the next major milestone in the Higgs search

167 was limits set by another collider in the US called the Tevatron.

168 The Tevatron was able to exclude a range here,

169 around 160 GeV here.

170 And by November 2011, the LHC had already radically narrowed the search.

171 The LHC has been able to rule out a big region

172 from 145...

173 ..quite far up.

174 It's been decades' worth of work

175 to gradually eliminate more and more of the space where the Higgs boson could be,

176 and now we are finally in this regime

177 where in the next couple of years

178 we might be able to close this gap

179 and finally know for sure whether it is there or not.

180 In November, that left a region of just 30 GeV

181 for the Higgs to be hiding in.

182 But this last remaining energy range is also the trickiest to search.

183 It is the area in which the unique signature of the Higgs

184 is most deeply buried

185 under the background noise of other particles created in the collider.

186 Not that the Higgs hunters were deterred.

187 The data is piling up and we know how to do it,

188 we just don't have enough data to tell you today what the answer is.

189 If I was to bet, I would probably put it at 130 GeV.

190 At the moment, probably somewhere around 120 GeV.

191 I would predict somewhere between 120 and 130 GeV.

192 I would put the Higgs somewhere close to 114 GeV,

193 because it is the most difficult place to look,

194 and we haven't found it yet.

195 That is a good question, because, you know,

196 you are assuming it actually exists,

197 which I am starting to believe it probably does not exist.

198 I'm really oscillating between thinking it is clearly there,

199 and then thinking, no, it's not going to turn up, is it?

200 Yeah, I don't know,

201 I think I have decided not to have a strong opinion.

202 I keep trying not to.

203 In almost every way, I think it would be more exciting

204 to prove it doesn't exist.

205 Yeah, it would be a longer-term bigger result, I think,

206 the negative result would have a longer-term bigger impact,

207 because it would really put us back to the drawing board.

208 On the other hand, in the short-term, it'd be disappointing

209 because a positive result is positive.

210 You'd like to see that. I don't think that's true at all.

211 I think a negative result, even in the short-term, would be more exciting.

212 It's the opposite of what people expect, right?

213 It's like... It'd be a lot more fun.

214 The experimental physicists here at CERN

215 have already put some of the ideas of their colleagues,

216 the theorists, to the test, and not all the results have been positive.

217 It's a whole bunch of theoretical models and papers.

218 There's been a bonfire of them since the LHC started.

219 There are whole swathes of potential speculation

220 that are now pointless. They're obviously a dead end

221 because the data says this.

222 But what's at stake with the Higgs isn't just one particle,

223 however elusive, or any old theory.

224 The Higgs is the cornerstone for the most successful and all-encompassing

225 description of how our universe works that there is.

226 Working this beautiful model out

227 has been one of the great achievements of theoretical physics,

228 and Frank Wilczek was one of the key contributors.

229 Hi. Welcome. Come in. Yeah, that'd be great, thank you.

230 I'll show you our library, living room, trophy room.

231 A lot of puzzle books, most of which I've worked through.

232 I'm a big puzzle man.

233 Here are the awards and trophies that have found their way here.

234 This is the Nobel Prize medal and here's one for you. Thank you.

235 Are these ones edible?

236 Yes, more or less. Anyway, I intend to eat one.

237 And...

238 ..you'll notice that...

239 ..not only in this room but everywhere, there are little toys.

240 A lot of what I do is really just play.

241 I mean, I play with the equations, ideas.

242 HE LAUGHS

243 And all that puzzling won Frank a Nobel prize

244 for his contribution to what's called

245 the Standard Model Of Elementary Particles.

246 Well, what have we got here?

247 It looks like an instrument of torture for the mind.

248 The Standard Model is essentially an understanding of how all the pieces

249 of the universe fit together, except for gravity.

250 A mind-boggling project.

251 This is going to be a hell of a puzzle to figure out.

252 All right. Now, a promising start. HE LAUGHS

253 'We think the Standard Model contains all you need,

254 'in principle, to describe how molecules behave,

255 'all of chemistry, how stars work, all of astrophysics.

256 'Not only how things behave, but what can exist.

257 'These are the rules of the game.'

258 The ingredients of the Standard Model are of three basic sorts.

259 There's what you might broadly call matter.

260 That's sort of lumps of stuff that have a certain degree of permanence

261 and these are on the one hand quarks.

262 They include the building blocks of protons and neutrons

263 and atomic nuclei.

264 And leptons.

265 The most prominent lepton in everyday life is certainly the electron.

266 So those are matter particles.

267 On the other side we have what you might call force particles,

268 or force mediators.

269 These particles are more like lumps of energy

270 and they transmit the forces that bring the matter particles to life,

271 like the photon, which carries the electromagnetic force.

272 The gluons that carry the strong force,

273 which holds the nuclei of atoms together,

274 and the W and Z bosons

275 that are responsible for the weak force governing radioactivity.

276 Every one of these particles has now been found experimentally.

277 There's just one pesky missing piece to the model

278 that they're searching for so intensively at CERN.

279 The Higgs.

280 In order to reconcile the beautiful equations

281 with the not quite as beautiful observations,

282 we need to find out what that piece is

283 and its properties and see if it really fits into a nice pattern

284 and completes the Standard Model.

285 We need experimental information

286 and this is usually called the quest for the Higgs boson.

287 This is why finding the Higgs is such an obsession among physicists.

288 If they do, it will be the vindication of this beautiful model.

289 And if not, they'll have to fundamentally rethink

290 their understanding of how the universe is put together.

291 In a way, finding the Higgs will be the completion of a dream.

292 Not finding it will be the start of a new one.

293 Imagine that the Standard Model is the car and the Higgs is the engine

294 and it's running, and imagine you find a car and then you open

295 and see no engine, so it might be more interesting than the car with an engine.

296 If you find that the car is running without an engine,

297 it's more interesting but it's kind of...

298 "What did I do in the last 20 years?" You know?

299 Do I believe in the Higgs? I... I think so.

300 I believe there's something that we're missing

301 and hopefully it's the Higgs, because...

302 it fits our model very nicely.

303 There are other possibilities, so I wouldn't discount those completely

304 but I think this is the best explanation we have so far.

305 Ask me in a year's time and I might give you a different answer.

306 It's October 2011 in the Atlas Control Room,

307 the nerve centre of one of two detectors at CERN

308 intensively searching for the Higgs.

309 Scientists here are avidly collecting data

310 from the billions of collisions, to comb for evidence of the boson,

311 because you can't simply spot it directly.

312 Almost as soon as it's created, it decays into other particles,

313 leaving just a trace of its existence.

314 The only way scientists can tell if a Higgs boson was there or not

315 is by looking for a statistical anomaly,

316 some blip in the measurements that they can't otherwise account for.

317 Seeing one picture like that isn't sufficient,

318 because there are other things that can look like the Higgs.

319 But if you get a bunch of them and you plot them, that's what we do,

320 that's our job, we put together all these tracks

321 and we say, "What mass of a particle would produce that?"

322 And then we look at them all and if we see a bump,

323 some little statistical anomaly there that's significant,

324 then we get excited, and then we go ask the other guys, "Hey, did you guys see that?"

325 Then we celebrate, but right now we've got a lot of work to do.

326 In the autumn, that intensive effort was being directed at the 30GeV

327 energy window that the Higgs could be hiding in.

328 We've covered a lot of range, we're travelling up a river,

329 we've checked all the different streams and we've narrowed it down

330 to some areas where it could be, and so that's where we're focusing

331 all of our energy, to look in those areas and see if we find it.

332 I think we're really on the brink of discovery.

333 But it's a slow process,

334 because it's all about crunching vast quantities of data.

335 One blip alone isn't enough, of course.

336 You need to be sure it isn't an error or fluke

337 and these anomalies can disappear almost as quickly as they arrive.

338 For experimentalists, these false alarms happen all too frequently.

339 You work on it day in, day out, so you get quite emotionally attached

340 to the state of these plots and numbers.

341 Especially if it's your plot. You want it to be your plot that finds the Higgs.

342 I realised at some point actually that it is genuinely...

343 I realised I found it genuinely stressful when plots get worse.

344 Yeah, that's right.

345 So many points can do that. When it get worse that makes me a little bit anxious and I think,

346 "This is insane." That's right,

347 and so you live in hope and then you often hit disappointment. Disappointed frequently.

348 It was in this state of perpetual tension that the scientists

349 working on the Atlas Detector met in November to discuss their latest set of results.

350 What's going on? They've just got started

351 and now we're going to get to the nitty-gritty of how things are actually going.

352 We don't have enough data, the statistics are fluctuating up and down.

353 You get excited about something and then more data,

354 it goes away and a bit more, it comes back.

355 It's all very tense at the moment, I'd say.

356 Fun. Does it feel like there's a real atmosphere

357 in terms of the search for Higgs closing in?

358 It's really weird because you're working on this more or less 20 hours a day

359 and it's been going on for a long time, so it becomes almost routine,

360 and then you get a meeting like this where it all

361 comes together and people go, "This is really exciting again."

362 This isn't one of those moments where people remember why we're here.

363 Can we come in? No.

364 In fact, the guy just said, "The BBC are outside.

365 "Be nice to them at the coffee break, tell them what they want to know."

366 The spokesperson was in there and said, "Don't tell them anything!"

367 The intense secrecy was because of the competition between the LHC's different detectors

368 to find the Higgs first and the provisional nature of the results.

369 What nobody was aware of at the time,

370 was that a small blip in the data that Atlas researchers had seen

371 would ultimately turn into something far more significant.

372 The hunt for the Higgs may be the most high-profile work going on at CERN

373 but the £6 billion experiment is about far more than finding one boson.

374 Scientists here are using the particle accelerator to understand

375 some of the other great mysteries of the universe.

376 But there's one common problem that links the Higgs

377 with other work happening here and that of scientists around the world.

378 Many scientists hope that if the Higgs is found

379 it'll help resolve the paradox within our understanding

380 of the laws of nature.

381 And it's a rather fundamental one.

382 Science has given us a set of laws

383 that describe the world so accurately

384 that we can predict the motion of a coin tossed in the air,

385 because we understand the law of gravity.

386 We understand electromagnetism so well that we can use our GPS satellites

387 to locate your car to within a few inches.

388 We understand the nuclear force so well that we can predict

389 the future evolution of the sun itself.

390 The mathematics that's given rise to many of these great successes

391 has one consistent theme.

392 It's one we see around us every day.

393 It characterises our faces, the natural world

394 and tiny structures like viruses and even our DNA.

395 Symmetry.

396 In the Standard Model, symmetry rules.

397 The laws are dictated really in their form

398 by requiring tremendous amounts of symmetry.

399 That's how we found them.

400 But for all the power of symmetry in uncovering these fundamental laws,

401 there's a deep paradox at work.

402 If the laws of science are framed at their most perfect,

403 most symmetrical form,

404 then life cannot exist at all.

405 There'd be no mountains, rivers, valleys.

406 No DNA, no people, nothing.

407 A universe created along absolutely symmetric principles

408 would be in perfect balance, and would cancel itself out.

409 There'd be no mass, Higgs... or matter at all.

410 But here we are.

411 Our world is teaming with life and complexity,

412 and yet that seems to be incompatible with

413 perfection in our equations. By rights, we shouldn't be here.

414 This paradox about symmetry

415 lies at the heart of modern physics.

416 And it's crucial to understanding the significance

417 of the Higgs itself.

418 So what unites much of the work at CERN

419 is trying to resolve this problem with symmetry.

420 There's another group of scientists

421 who work alongside the Higgs hunters.

422 There are over 700 of them,

423 and they're searching for answers to this puzzle about symmetry.

424 So this canteen is very important, really.

425 It's one of the main working places at CERN.

426 You see a lot of big names down here -

427 if you wait long enough you'll come across a Nobel Prize winner

428 during the day.

429 Peter Clarke is one of the scientists working

430 on the Large Hadron Collider's LHCb experiment,

431 along with his colleague from the University of Edinburgh, Conor Fitzpatrick.

432 Their field of study

433 is the weird symmetric mirror world of antimatter.

434 A substance that's as real as matter, but its opposite...

435 ..and rather more elusive.

436 The geek in everyone still feels a bit excited about the concept of working with this stuff.

437 It's not something the public sees from day to day life,

438 and it's one of the few things you can only see at CERN.

439 Antimatter may sound like the stuff of science fiction.

440 But since it was first proposed as a concept 80 years ago,

441 scientists have been creating it in experiments.

442 The very idea of antimatter emerged from a revolutionary

443 piece of mathematics, with symmetry at its heart.

444 It said that for every particle of matter,

445 there should be a corresponding one of antimatter.

446 Once one's thought about the symmetry of the theories,

447 and realised that antimatter must exist,

448 you then think it's absurd that there wouldn't be antimatter

449 or the possibility to create antimatter.

450 Which is why it's so surprising that world we live in is entirely made of matter.

451 Because the theory posed a puzzle:

452 when matter and anti-matter meet, they destroy each other completely.

453 Equal amounts of each would leave nothing but energy.

454 If the laws of science are expressed in their most perfect form,

455 then life cannot exist at all.

456 Clearly, all the matter WASN'T destroyed by antimatter.

457 After all, we see around us far more matter than antimatter

458 in the universe today.

459 Just how this could have happened is something that Peter, Conor

460 and the other scientists on the LHCb experiment are trying to understand.

461 So they're using the Large Hadron Collider to create some

462 pairs of matter and antimatter particles of their own,

463 to study what could have happened

464 in that crucial first second of the universe.

465 We're currently in the LHCb control room.

466 This is colloquially referred to as "the pit" -

467 100 metres below us right now is the LHCb experiment itself.

468 LHCb is one of the four detectors sited around the collider.

469 When the two beams of protons meet in a head-on collision,

470 recreating the energy levels just after the Big Bang,

471 it records the particles that are formed.

472 We can see antimatter being created in our detector,

473 so the difference between matter and antimatter is that they're differently charged.

474 So these two green tracks here,

475 in a magnetic field they're going differently, so one of them

476 has to be matter, and one of them has to be antimatter.

477 It's kind of cool that we can see it right here in an event on the screen.

478 Combing through the wreckage of billions of collisions,

479 and building on the work of previous particle accelerators,

480 scientists here have been in search of ways

481 in which matter and antimatter behave differently.

482 And they've managed to observe one -

483 a crucial breaking of symmetry

484 in the behaviour of matter and antimatter versions

485 of particles called B mesons.

486 So I'll give you one example of the way

487 we observe the difference between matter and antimatter.

488 This is perhaps the simplest example to visualise.

489 We can observe how B mesons created in LHCb decay to particles,

490 and how anti-B mesons decay to antiparticles.

491 We can count the rate at which this happens,

492 the number of times it happens, and we do this.

493 We observe the particles decaying 7,000 times,

494 and the antiparticles 6,000 times.

495 And if matter and antimatter did not have this asymmetry,

496 it would just be an equal number of times.

497 So this difference of 1,000 is an absolute clear manifestation

498 of the asymmetry between matter and antimatter.

499 So far, researchers haven't been able to find

500 enough instances of this asymmetry

501 to explain all the matter we know IS in the universe.

502 But one thing is clear. The reason we exist,

503 is because the perfect symmetry scientists believe was once there

504 between matter and antimatter must somehow have been broken.

505 And symmetry breaking is at the heart of scientists' understanding

506 of how the Higgs came to give mass to everything in the first place.

507 The theory goes that there was a moment after the Big Bang

508 when the Higgs field appeared.

509 And this split apart a perfect symmetry

510 between two of the fundamental forces of nature.

511 And the Higgs gave the particles of these forces different masses.

512 And at the same time, it gave mass to all the other particles.

513 The Higgs Boson and the Higgs field is basically what does this symmetry breaking.

514 So the whole idea that our theories

515 revolve around symmetries and broken symmetries -

516 the Higgs is kind of the linchpin of that.

517 It's this unique prediction of this kind of idea,

518 and without it, we're back to the drawing board,

519 but with it, if we see it,

520 it's a stunning prediction of this idea of symmetry

521 and broken symmetry somehow lying behind the way the universe works.

522 The Higgs allows the symmetry in scientists' equations

523 to be broken in the real world.

524 Finding it would be a vindication

525 of their whole approach to understanding the universe.

526 That's why it's become

527 such a defining quest in modern physics.

528 Tuesday 13th December 2011

529 was a day with the potential to change physics history.

530 NEWS: 'Scientists at the Large Hadron Collider near Geneva

531 'are expected to announce later...'

532 '..are expected to present preliminary evidence today...'

533 '..will confirm whether the current theory of particle physics is correct.'

534 Since November, a lot more data had been crunched,

535 ahead of an important meeting.

536 It was the end of year report, where the experiments analysed

537 the data we collected during 2011, and reported on the Higgs search.

538 And I guess everyone knew that either the mass range

539 the Higgs could be in was going to shrink down,

540 possibly to nothing, or some kind of hint would pop up

541 that there was something there.

542 What was special about this meeting was that it would bring together

543 data from two independent detectors at CERN.

544 The data from Jon and Adam's Atlas detector,

545 and a second one - CMS.

546 But neither team knew in advance what the other had discovered,

547 and the atmosphere on both sides was electric.

548 It was ridiculous... Yes.

549 Very er... almost frenzy, I don't know.

550 There were having their breakfast in the lecture theatre at 9 o'clock,

551 to be sure they'd get a seat for the seminar at 2 o'clock.

552 The room holds about 600 people,

553 and it was full two hours before the talk started.

554 There were rumours on the internet,

555 and obviously people talk to each other,

556 so I think, yeah, this idea that something exciting

557 was about to happen was building in the community at least. All got a bit out of hand, really.

558 By late afternoon, it was clear that the hunt for the Higgs had closed in.

559 NEWS: 'Scientists hunting for the elusive Higgs Boson

560 'say they've discovered strong signals that it exists.'

561 'Scientists say they've uncovered signs of the elusive Higgs Boson,

562 'known as the God Particle.'

563 'Researchers presented results from two independent experiments...'

564 '..evidence which helps them move closer to the building blocks of the universe.'

565 What had emerged during the meeting was that a potential

566 signal of the Higgs had been spotted in both experiments.

567 And crucially, in practically the same place.

568 It was very exciting.

569 People were getting the Atlas data and the CMS data

570 and going, "Do they really see the same thing?" and all this.

571 It was a lot of fun, actually, and a major step forward.

572 The results weren't definitive,

573 but in the month between November and December

574 the data plots had evolved significantly.

575 So the announcement was that the LHC,

576 with the new data from the whole of 2011, is able to expand

577 the area that it can exclude the Higgs from.

578 The new lower limit has risen to 115 GeV.

579 And the new upper limit has dropped to 127 GeV.

580 So the really exciting thing was that the reason the LHC experiments weren't able to exclude

581 anything inside this remaining window, is that in fact they see an

582 excess of events. The early signs of the Higgs Boson, if it's there.

583 And the excesses were in practically the same place.

584 CMS observed one at 124 GeV,

585 and Atlas one at 126.

586 So this is really a tantalising hint that the Higgs Boson

587 might exist, and it might have a mass of around 125 GeV.

588 I think a lot of people will be really interested to see what

589 happens in this region when we add more data in 2012.

590 That's going to be really exciting to follow.

591 For all the buzz surrounding the Higgs,

592 scientists can't claim to have officially discovered

593 this elusive particle just yet.

594 And there are some outstanding questions

595 about WHY it would have this mass.

596 But with such promising data so far,

597 it's hard not to be enthusiastic.

598 Six months ago I would have said that there probably is no Higgs.

599 It's a neat idea, but what are the chances of nature

600 actually doing what we think it should do?

601 But now I think maybe it has. This is kind of remarkable.

602 What's clear, though, is that with four times the amount of data

603 expected out of the LHC next year,

604 this long-standing question will be finally resolved.

605 I mean, there will be a day, some time next year, where

606 we will go in not knowing whether the Higgs Boson exists or not,

607 and we will come out... And that that will be a fact, you know -

608 we will know one way or the other, and our knowledge of the universe will have expanded.

609 In a big way, as well. I mean... Yeah.

610 It may not be everyone's idea of a great time,

611 but what we're seeing is physics textbooks being written.

612 And to me, having studied physics for so long,

613 and known what's in those textbooks, and taught people

614 from those textbooks, to see new pages being written that will never

615 be unwritten, this is something new we know, that we didn't know before

616 that we will always know afterwards. That is really exciting.

617 If the Higgs is confirmed at last,

618 then it'll open a new chapter

619 in our understanding of how the universe works.

620 Scientists plan to use the completed standard model

621 as the foundation for an even deeper description of the universe,

622 one based on the idea of symmetry and its breakage.

623 That could take our knowledge of the cosmos even further back

624 into that crucial first second of existence,

625 right to the moment of the big bang itself.

626 It's long been a dream of theorists to wind the clock back to the instant of creation,

627 a place, so far, no machine has been able to go.

628 Here, they believed they'd find a moment of absolute symmetry.

629 The state of perfect symmetry

630 is very similar to the state of perfect balance.

631 Think of a spinning top.

632 It exists in a state of perfect rotational symmetry.

633 No matter how you rotate, everything looks the same.

634 Just like with the spinning top, at this instant of creation,

635 everything in the universe would've been the same.

636 There'd be no distinction between gravity and electromagnetism,

637 light and dark, matter and forces.

638 But perfection can't last.

639 The slightest imperfection, the slightest little defect,

640 will cause it to vibrate and fall to a lower energy state.

641 Symmetry has been broken.

642 Within a fraction of a second of the big bang,

643 physicists believe the absolute symmetry of the universe was shattered by a tiny fluctuation.

644 The forces split apart.

645 The particles of the standard model became distinct.

646 This fall from perfection was what allowed us to come into being.

647 Everything we see around us is nothing but fragments of this original perfection.

648 Whenever you see a beautiful snowflake, a beautiful crystal

649 or even the symmetry of stars in the universe,

650 that's a fragment, that's a piece of the original symmetry at the beginning of time.

651 By unifying the fragments,

652 physicists think they'll find the ultimate key

653 to how the universe was born.

654 The Higgs is a vital stepping stone in this mission.

655 But in their quest for unification,

656 theoretical physicists have taken the idea of symmetry

657 to a new, extraordinary level.

658 When James Gates came to study at MIT,

659 he was keen to unlock the secrets of the universe.

660 And he was prepared to push the boundaries of his thinking a little further than most.

661 The universe and we are intricately tied together.

662 This idea of unity turns out to be one of the most powerful driving themes in physics.

663 And it keeps getting us to look for deeper and deeper connections.

664 Ultimately, perhaps we exist because the universe had no other choice.

665 He began with the standard model -

666 the collection of building blocks of matter

667 and the forces that hold them together.

668 Could these two very different groups of particles

669 be connected in some more fundamental way?

670 So, when we find something in nature that doesn't have a symmetry,

671 we always ask the question, "Why?"

672 and then we go one step further and ask the question, "What if?"

673 It was the asking of this "what if?" question

674 that drove the construction of supersymmetry

675 which had an incredible resonance for me when I was a graduate student.

676 I saw one more beautiful balance that we could put in nature.

677 James became one of the pioneers

678 of a powerful new mathematical theory called supersymmetry.

679 Using symmetry in equations had previously led to the discovery of antimatter.

680 Thes new ones suggested there was a hidden world of particles no-one had suspected.

681 Mathematics leads us to find things we didn't know were there before.

682 Supersymmetry is an example of that.

683 We know about ordinary matter.

684 The maths leads you on to discover super-matter and super-energy.

685 The theory took everything we thought we knew about,

686 even the Higgs, and doubled it...

687 ..giving every matter particle a force partner

688 and every force particle a matter partner.

689 These heavier, supersymmetric twins were labelled sparticles.

690 So, once you believe this maths that says there's more to existence

691 then you have to wonder what these other things are.

692 You have to name them, at the very first step.

693 So, in nature, there's a thing called the electron.

694 The maths says it has a superpartner called the selectron.

695 Muon - there'd have to be the smuon.

696 Photon - there'd have to be a photino.

697 Quark - there'd have to be squarks.

698 Z particle - there'd have to be zino.

699 W particle - there'd have to be a wino.

700 And that's how supersymmetry works.

701 According to supersymmetry,

702 matter and forces aren't so distinct after all.

703 There's a grand symmetry between them.

704 But we can currently see only one partner from each pair.

705 However strange it seems,

706 this theory has gained widespread support from theoretical physicists...

707 ..not just for the beauty of its equations

708 but for what it might help explain.

709 When supersymmetry began as a topic of discussion,

710 no-one realised what it can do.

711 It turned out that, studying the mathematics,

712 we get a firm foundation for the existence of everything.

713 One of the great attractions of supersymmetry is it helps to resolve a niggling problem

714 with the existence of the Higgs particle,

715 alleviating the need for mathematical fudges

716 in the standard model to fix its mass.

717 This object called the Higgs? The mass of this could fluctuate,

718 except if there's supersymmetry and that stabilises the mass.

719 Supersymmetry makes the mass of the Higgs more natural, more stable, less of a wild coincidence.

720 It could even help explain why there's more matter than antimatter in the early universe.

721 Supersymmetry is the theory that, if it were true,

722 could allow the rates of matter and antimatter interactions early on

723 to be great enough to explain the asymmetry we need in the early universe.

724 Supersymmetry pieces together more broken fragments from that first second of existence.

725 I very much want supersymmetry,

726 because it's a beautiful thing, by any standard

727 and would take our understanding of nature to a new level.

728 So, I want that.

729 But, so far, it's just a theory, with no experimental data

730 to support it.

731 At least, not yet.

732 That's where the £6 billion experiments at CERN

733 may really usher in a revolution.

734 Because they're hunting for evidence of supersymmetry.

735 So, here we are now, 100 metres underground,

736 where the LHCB detector is installed.

737 Since the accelerator is stopped now for a few days, we can actually go in and see the detector.

738 Richard Jacobsson is in charge of the operation of the detector

739 that may give the first clues about supersymmetric particles.

740 So, this is really where the dreams of theorists meet reality.

741 Theorists, they invent new ideas as they go

742 and our job as experimentalists is to actually find out

743 which of these theories are definitely wrong

744 and which are the ones we can establish, measure,

745 that actually correspond to what we measure in the experiment.

746 So far, not only have they found no evidence of the photinos,

747 squarks or other sparticles predicted by the theorists,

748 they've even ruled out the possibility of them

749 at some of the energies theorists were hoping they'd be.

750 Throughout this year, we've recorded more than ten billion reactions between protons.

751 By studying them very precisely, we've been able to sort of exclude certain versions of supersymmetry.

752 For the theorists, this means they have to look in a different direction.

753 But the first, tantalising glimpse of the Higgs will have come as an encouragement to scientists here,

754 because the mass of the Higgs

755 determines the mass of the sparticles.

756 And if they were too heavy, the LHC would be simply unable to create them.

757 Fortunately, the mass of the Higgs they have hints of

758 means evidence of the sparticles should show up in this machine.

759 That's IF they exist.

760 JAMES GATES: LHC is up and running. So far, there's no sign of superparticles.

761 If we find supersymmetry in experiments,

762 for me, personally, it will mean that I have not wasted my entire research career

763 because this is the one question, as a young scientist, I decided had my name on it to study.

764 I'm starting to get nervous.

765 You know...

766 Er...

767 So, there were a lot of people who predicted supersymmetry was just around the corner,

768 or something else, that as soon as LHC turned on, they'd see spectacular effects,

769 or that the Higgs particle would be heavy. Those were all wrong.

770 So far, nothing I believed in has been proved wrong and a lot of the competition has gone up in smoke.

771 But the crunch time is coming.

772 They're going to be capable of seeing things I've predicted or want

773 and we'll see. It's in the hands of God or CERN or something.

774 Now it's make or break time.

775 For the scientists involved,

776 pushing the frontiers of knowledge is a roller coaster ride.

777 And, with the Large Hadron Collider, the journey has only just begun.

778 This machine has opened the door to physics, above this key energy scale in nature,

779 where the symmetries of nature change fundamentally.

780 You don't get the key, open the door, go, "Well, that was nice," then close the door.

781 You see what's happening.

782 That's what we'll be doing in the next many years.

783 If every theory was like a room,

784 it's like we looked in the first one down the corridor,

785 and already we found something exciting, so now we can't wait to look in all the others, right? Yep.

786 Yep.

787 There's loads more stuff we'd like to look for at the LHC,

788 like supersymmetry, extra dimensions...

789 Quantum gravity.

790 New fundamental forces.

791 Substructure inside quarks, black holes...

792 Miniature black holes. Think of your favourite theory and double it...

793 The possibilities are endless. Yeah, absolutely.

794 To put this into perspective,

795 I think the last time we stood in such an exciting place

796 was 1905, when Einstein discovered special relativity

797 and announced the most famous equation in physics - E=mc2.

798 Because if the Higgs is confirmed,

799 it's about much more than just a spectacular discovery.

800 It'll also open a new chapter in physics, ask new questions,

801 setting off the search for an even deeper understanding of nature.

802 But we simply can't say where THAT search will take us.

803 Subtitles by Red Bee Media Ltd

804 E-mail subtitling@bbc.co.uk