The DELPHI experiment at the LEP accelerator at the CERN laboratory

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1 Th DELPHI xprimnt at th LEP acclrator at th CERN laboratory Part 1. Th LEP acclrator Part 2. Th DELPHI xprimnt Part 3. Particl physics rsarch at LEP

2 Th LEP acclrator Th study of collisions btwn lctrons and positrons. LEP 1 : Th collision nrgy = 91 GV = Z LEP 2: Th collision nrgy = 209 GV > 2W 2

3 Th largst acclrators in th world - LEP (CERN) 46 GV 104 GV hadrons Z 0 hadrons Lngth: 27 km (4184 magnts) Exprimnts: DELPHI, OPAL, ALEPH, L3 q q GV 104 GV HERA (DESY) + 30 GV hadrons + γ Lngth: 6 km (1650 magnts) Exprimnts: H1, ZEUS q g q g q g 920 GV p p 1000 GV TEVATRON (FERMILAB) q g q g q g hadrons g hadrons Lngth: 6 km (990 magnts) Exprimnts: CDF, D0 q g q g q g 1000 GV p 3

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10 LEP 1 LEP 2 In ordr to incras th collision nrgy on had to build 240 suprconducting radio-frquncy cavitis. Acclrating gradint = 6 MV / m Frquncy = 352 MHz Th nrgy lost du to synchrotron radiation is 2.3 GV / turn Radio-frquncy acclrating voltag has to b 2.3 GV / turn Yar: Collision nrgy: (GV) 10

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12 Th collision nrgy At LEP th collision nrgy could b dtrmind with a vry high accuracy: GV with an rror of GV Things which affctd th nrgy of LEP: 1. Th lvl of th watr in th lak! 2. Th moon! 3. Th trains to Paris! 12

13 Gological shifts E (MV) 0 Enrgy calibrations Horizontal Orbit (X ARC ) Lak lvl fit During 1993 th LEP nrgy was obsrvd to chang with tim. Days Part of th chang was du to th watr lvl in lak Gnva which causd small gological shifts of th acclrator. Rainfalls and th watr tabl in th Jura mountains also affctd th LEP nrgy. 13

14 Tids E [MV] 5 0 Novmbr 11 th, 1992 Earth tids causd by th moon will produc small distortions of th arth s crust :00 3:00 7:00 11:00 15:00 19:00 23:00 3:00 This can affct th acclrator so that th lctrons orbit chang. E [MV] 5 August 29 th, 1993 Octobr 11 th, 1993 An orbit chang of 1 mm will chang th nrgy with about 10 MV :00 13:00 15:00 17:00 19:00 21:00 23:00 18:00 20:00 22:00 24:00 2:00 4:00 6:00 8:00 Daytim 14

15 Bampip currnt Th trains from Gnva to Franc causd parasitic currnts on th LEP bampip. Ths currnts (1 A) affctd th magntic fild in th LEP magnts and this changd th nrgy. Vacuum Chambr Currnt Corrlation LEP IP3 IP2 CERN Bllgard IP4 LEP IP1 IP5 SPS IP8 Myrin Zimysa Trains 1 km IP6 IP7 airport Rivr La Vrsoix Cornavin Gnva Lausann Lac d Gnv Lak Voltag on rails [V] Voltag on bampip [V] Bnding B fild [Gauss] RAIL LEP bam pip LEP NMR Gnv TGV 16:50 16:55 Myrin Zimysa Tim 15

16 Th DELPHI xprimnt Forward Chambr A Forward RICH Forward Chambr B Forward EM Calorimtr Forward Hadron Calorimtr Forward Hodoscop Forward Muon Chambrs Surround Muon Chambrs Barrl Muon Chambrs Barrl Hadron Calorimtr Scintillators Suprconducting Coil High Dnsity Projction Chambr Outr Dtctor Barrl RICH Small Angl Til Calorimtr Quadrupol Vry Small Angl Taggr DELPHI STIC Tracking dtctor Hadronic calorimtr Elctromagntic calorimtr Innr Dtctor Vrtx Dtctor Tim Projction Chambr Muon dtctor Bam Pip 16

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18 Crosssction Z o + Collision nrgy + µ - - Z o µ + + τ - - Z o τ + 18

19 + - - Z o + DELPHI Intractiv Analysis Bam: 45.6 GV Proc: 1-Oct-1991 Run: Evt: 2958 DAS : 25-Aug :46:38 Scan: 4-Dc-1992 Act Dact TD TE TS TK TV ST PA ( 37) ( 35) ( 0) ( 4) ( 0) ( 0) ( 0) ( 0) ( 1) ( 0) ( 3) ( 0) ( 0) ( 0) Hadronic calorimtr Muon spctromtr Magnt Elctromag. calorimtr Chrnkov TPC Y Z X 19

20 + µ - - Z o µ + DELPHI Intractiv Analysis Bam: 45.6 GV Proc: 1-Oct-1991 Run: Evt: 1417 DAS : 25-Aug :36:22 Scan: 19-Fb-1992 Act Dact TD TE TS TK TV ST PA ( 28) ( 29) ( 0) ( 2) ( 3) ( 0) ( 0) ( 0) ( 2) ( 0) ( 2) ( 0) ( 0) ( 0) Magnt Hadronic calorimtr Elctromag. calorimtr Chrnkov TPC Muon spctromtr Y Z X 20

21 + τ - - Z o τ + DELPHI Intractiv Analysis Bam: 45.6 GV Proc: 8-Mar-1992 Run: Evt: 581 DAS : 18-Jun :22:19 Scan: 29-Apr-1992 Act Dact TD TE TS TK TV ST PA ( 44) ( 48) ( 0) ( 9) ( 9) ( 0) ( 0) ( 0) ( 4) ( 0) ( 6) ( 5) ( 0) ( 0) Hadronic calorimtr Magnt Elctromag. calorimtr Chrnkov Muon spctromtr TPC Y Z X 21

22 + q - Z o q DELPHI Intractiv Analysis Bam: 45.6 GV Proc: 1-Oct-1991 Run: Evt: 3018 DAS : 25-Aug :47:02 Scan: 19-Fb-1992 Act Dact TD TE TS TK TV ST PA ( 93) (133) ( 0) ( 23) ( 18) ( 0) ( 0) ( 0) ( 13) ( 0) ( 23) ( 12) ( 0) ( 0) Hadronic calorimtr Magnt Elctromag. calorimtr Chrnkov Muon spctromtr TPC Y Z X 22

23 What dos a particl physicist do? Th building of dtctors Exampls: - Th TPC (Tim Projction Chambr) - Th STIC (Elctromagntic calorimtr) Analysis of th data from th xprimnt Exampls at LEP 1: - Luminosity - Studis of th Z-boson Exampls at LEP 2: - Studis of th W-boson - Sarch for nw particls 23

24 Th Tim Projction Chambr Chargd particl + E B E - A chargd particl ioniz th gas in th cylindr and th lctrons drift in an lctrical fild to th dtctors at th nds of th cylindr. Thr-dimnsional tracks can b rconstructd from th signals from th dtctors. 24

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26 Th calorimtric procsss An lctromagntic showr Air Lad 2 cm + γ γ Brmsstrahlung Photon - convrsions A hadronic showr 15 cm π Air Lad π π K π π π p K π 20 cm Hadron- Nuclon Intractions 20 cm 100 cm 26

27 STIC sid C DELPHI STIC TPC Microvrtx ID Jt Chambr ID Triggr Layrs STIC sid A STIC was two lctromagntic calorimtrs built by Lund in collaboration with physicists from 12 othr instituts in 6 countris. 27

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34 STIC sid C Luminosity DELPHI + TPC Microvrtx ID Jt Chambr ID Triggr Layrs - STIC sid A What is luminosity? Th numbr of vnts pr s = cross sction x Luminosity How is th luminosity masurd? By counting th numbr of vnts from a procss for which th cross sction can b calculatd. Which procss was usd at LEP? γ γ Bhabha Scattring 34

35 Th hadronic linshap of th Z-boson Th width of th Z-boson pak dpnds on th numbr of light nutrino spcis (N). + q σ = Z - Z o q Luminosity N=2 N=3 N=4 DELPHI Enrgy, GV 35

36 γ / Z o W - W + ν W - WW-vnts W + qq qq qq lν lν lν 46% 44% 11% 36

37 Th mass of th W-boson 2 qq qq = ( ) 46% ϕ Μ W 2 Μ W 2 P + P q q _ ϕ = 2 E E ( 1 - cos ) q q _ if m = 0 q ( 4-vctors ) vnts / 2 GV/c DATA WW (Mw = 80.35) ZZ QCD W mass [ GV/c 2 ] 37

38 Th W-cross sction + W + σ = WW Cross Sction (pb) W σ W DELPHI γ / (prliminary) Z o W - W + ν W - Luminosity GENTLE 2.0 (±2%) RacoonWW, YFSWW s (GV) 38

39 Evnts/0.05 Evnts/0.05 Th sarch for nw particls 150Basic ida: Unification s = of gravity GV with othr intractions by Backg. introducing 534 vnts nw compact obs. dimnsions of spac in 100 which only gravity propagats. Data Cross sc.: σ ( + - Grav. + γ ) dpnds on : 50 n - th numbr of xtra dimnsions M D - th fundamntal mass scal in th thory 0 Standard Modl: 100 s = GV n = 2 γg γνν _ γg 25 M D = 0.75 TV Extra dimnsions 549 vnts xp. 429 vnts obs. 452 vnts + xp. - γ Z o ν ν Evnts/ s = GV 563 vnts obs. 568 vnts xp E γ E bam x γ

40 Th sarch for Higgs vnts + H 0 bb ττ WW gg cc 74% 8% 8% 6% 4% - Z o qq νν µµ ττ 70% 20% 3% 3% 3% bb bb bb bb qq νν µµ ττ 40

41 14 Th mass spctrum of Higgs candidats ZZ and WW vnts that hav bn wrongly idntifid as Higgs vnts Expctd signal from Higgs dcays vnts/3 GV/c DELPHI E cm = GV L=224 pb -1 Data 16 MC 23.5 signal 3.25 mh=114 GV/c Mass (GV) M (GV/c 2 ) 41

42 Summary Th LEP acclrator was th largst acclrator th world has vr sn. DELPHI was on of th hug xprimnts that studid th collisions btwn lctrons and positrons. DELPHI has contributd much to our prsnt undrstanding of th standard modl. Th acclrator and th xprimnts hav bn dismantld but th physicists continu to analyz th data that was collctd. 42