Big bangs

Sci­en­tists be­gin to re­dis­cover our uni­verse

Down to Earth - - CONTENTS - VIBHA VARSH­NEY |

Othis year, bil­lions of N JUNE 3 col­li­sions oc­curred in a 27-km­long cir­cu­lar tun­nel be­tween Switzer­land and France. But this is not a cause for con­cern as these col­li­sions were part of the sec­ond sea­son of ex­per­i­ments at cern (the Euro­pean Or­ga­ni­za­tion for Nu­clear Re­search), which is the world’s lead­ing lab­o­ra­tory for par­ti­cle physics.

The first sea­son of col­li­sions at eight TeV (ter­a­elec­tron­volt) con­firmed the pres­ence of Higgs bo­son, the elu­sive par­ti­cle that seems to pro­vide mass to all other par­ti­cles. In the sec­ond sea­son,pro­ton beams will be made to col­lide at 13 TeV,nearly dou­ble the energy at which ex­per­i­ments were car­ried out in the first sea­son. Re­searchers hope these ex­per­i­ments would fur­ther in­crease our un­der­stand­ing of sub­atomic par­ti­cles.By re­leas­ing the beams of pro­tons into the Large Hadron Col­lider (lhc) in both di­rec­tions, and con- trolling them with pow­er­ful su­per­con­duct­ing mag­nets,the re­searchers man­aged to gen­er­ate sta­ble beams. Re­searchers now have a source for a truly new set of data. “Let’s see what they will re­veal to us,”says Rolf Heuer, di­rec­tor-gen­eral of cern.

When pro­tons with high energy col­lide, they frag­ment into the most ba­sic of its com­po­nents. These are be­ing de­tected by sen­sors placed around the lhc. “It is a big jump from eight TeV to 13TeV. Par­ti­cles could be­have one way at eight TeV and in another way at 13TeV,”says Varun Sharma,a PhD stu­dent at cern. Sharma works on the Com­pact Muon So­le­noid (cms), one of the seven par­ti­cle de­tec­tors that helps see the sub­atomic par­ti­cles pro­duced dur­ing the col­li­sions. Sharma is hop­ing to study the sub par­ti­cles of quarks—one of the fun­da­men­tal

par­ti­cles in physics. These sub par­ti­cles or pre­ons have been dis­cussed the­o­ret­i­cally and their pres­ence would be con­firmed if their sig­na­ture can be de­tected.

Physics phe­nom­ena

Dur­ing the sec­ond sea­son, seven ex­per­i­ments are planned. De­tec­tors at­las, cms,alice and lhcb will look at a wide range of physics phe­nom­ena—from Higgs bo­son and dark mat­ter to the dif­fer­ence be­tween mat­ter and an­ti­mat­ter. Ex­per­i­ments like totem would use de­tec­tors to mea­sure the pro­tons as they emerge from col­li­sions.The lhcf experiment would mea­sure neu­tral par­ti­cles.The moedal experiment would look for mag­netic mono­poles to in­ves­ti­gate the pos­si­bil­ity of ex­tra di­men­sions and the na­ture of dark mat­ter.(see box: ‘Data scope’)

“We strongly be­lieve that some­thing un­known is just around the cor­ner,”says Ehud Du­chovni of Weiz­mann In­sti­tute of Science, Is­rael.This makes the re­search an ex­cit­ing ad­ven­ture,he adds.Michael Hance,a re­searcher at the Lawrence Berke­ley Na­tional Lab­o­ra­tory in the US,who works on the at­las experiment,is look­ing at events with bosons that may come from the de­cay of some heavy new par­ti­cle. “Dur­ing the first-run of the lhc,we searched for ev­i­dence of physics be­yond the Stan­dard Model but un­fortu- nately,we did not see con­vinc­ing signs of any­thing new. Dur­ing the sec­ond sea­son, we hope to find out­side of what the Stan­dard Model pre­dicts.This could be a new par­ti­cle or a new force of na­ture,”says Hance.

“The uni­verse is com­posed of ap­prox­i­mately 68.3 per cent dark energy, 26.8 per cent dark mat­ter and 4.9 per cent or­di­nary or vis­i­ble mat­ter.What we know about the uni­verse be­longs to the last 4.9 per cent,” says Bra­jesh Choudhary, pro­fes­sor, depart­ment of physics and as­tro­physics,U niver­sity of Delhi. “The field of re­search is wide open when it comes to the re­main­ing as­pects of fun­da­men­tal physics,”he adds.

Huge amounts of data would be gen­er­ated dur­ing the sec­ond sea­son—150 mil­lion sen­sors are tak­ing im­ages 40 mil­lion times per sec­ond. “This is just the be­gin­ning,”says Markus Schulz, who works on dis­trib­uted com­put­ing at cern. The quan­tum of data gen­er­ated is ex­pected to in­crease from 25 peta bytes (PB) per year in 2012 to 400 PB per year by 2024,pro­vid­ing sci­en­tists a wealth of in­for­ma­tion to en­rich our un­der­stand­ing of the uni­verse. While it is not yet clear how the “new physics”would help in pre­cise terms, the re­search has long-term value.As Sharma says,“We can use elec­tric­ity be­cause we un­der­stand elec­trons.We are al­ready us­ing pro­tons to treat can­cer...”

SEC­OND WATCH: ALICE Run Con­trol Cen­tre dur­ing the first 13 TeV pro­ton col­li­sions with sta­ble beams, on June 3. (inset) One of the first col­li­sions with "sta­ble beam" at 13 TeV recorded by de­tec­tor, CMS

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