G. Hanson et al. Phys. Rev. Lett. 5 (1975) 1609 Physcs Colloquum July 7th, 008 Evdence for Jet Structure n Hadron Producton by e + e - Annhlaton Contents: 1. Introducton. Exerment at SLAC. Analyss 4. Results 5. Summary Suzuk Kento Shbata lab. 1
1. Introducton jet Ths aer reorts the frst evdence for the exstence of the hadron jet n e + e - annhlaton. Jet : collmated srays of hadrons jet e + q q e - jet vrtual hoton e + e + γ * q + q jet + jet e + γ* q At large value of E c.m the hadron jets n e + e - annhlaton can be observed. e - q jet
. Exerment at SLAC 50 ~10 The exerment was carred out at the SPEAR storage rng of SLAC, USA. beam Electron-ostron collder Data were collected at E c.m. of.0,.8, 4.8, 6. and 7.4 GeV. (The dameter of the col of the magnet) m jet
. Analyss (1) Shercty( 球形指数 ) Choose the axs whch mnmzes the value of by teraton. where the summaton s over all detected artcles : the transverse momentum wth resect to the chosen axs. The shercty S determnes how jet-lke an event s. ( mn S = ) r Chosen axs ( s the momentum of each artcle.) S 1 S 0 4
() Two models : jet model and hase-sace model Monte Carlo smulaton s an mortant method for comarson wth data. Smulaton based on the two models Isotroc hasesace model Jet model () The angular dstrbuton of the jet axs The angular dstrbuton of the jet axs s exected to be dσ dω 1+ α cos θ + P α sn θ cos ϕ ( P : the olarzaton of the beams ) 5
4. Results (1) Mean Shercty vs. Center of Mass Energy Phase-sace model The mean S of the data and the two models The mean S of the data decreases wth E c.m.. The mean S of the jet model also decreases wth E c.m.. But the hase-sace model ncreases wth E c.m.. Mean Shercty Jet model The jet model agrees wth the data. But the hase-sace model does not. E c.m. ( GeV ) 6
() Shercty dstrbuton of events The data The eak of S dstrbuton shfts to lower value at hgher energes. The two models Jet model : the eak of S dstrbuton shfts to lower value at hgher energes. Phase-sace model : the eak of S dstrbuton stays around 0.4. ( Small shercty : collmated hadrons ) At E c.m. = 6. and 7.4 GeV The jet model agrees wth the data. But the hase-sace model does not. The fgures n ths age and revous age ndcate that the jet model agrees wth the data. Number of Events (a) E c.m =.0 GeV (b) E c.m =6. GeV (C) E c.m =7.4 GeV 0 0. 0.4 0.6 0.8 Shercty S Ths s an evdence for jet 7
() Another evdence for jet The lane of the storage rng Jet axs At 7.4 GeV the beam s transversely olarzed due to synchrotron radaton. P = 0.47 ± 0.05 The angular dstrbuton of the jet axs s exected to be dσ 1+ α cos θ + P α sn θ cos dω Exermental data : The angular dstrbuton of the jet axs ndeed has deendence on azmuthal angle φ. ϕ Number of Events e + φ : the azmuthal angle of the jet axs wth resect to the lane of the storage rng. φ Azmuthal Angle of Jet Axs φ (degrees) θ ( 50 <θ< 10 ) e- Another evdence for jet 8
5. Summary Ths aer reorts the frst evdence for the exstence of the hadron jet. The hadron jet s roduced n e + e - annhlaton. The exerment was carred out at SLAC-SPEAR. Data were collected at E c.m. of.0,.8, 4.8, 6. and 7.4 GeV. Shercty s an mortant quantty for the analyss. The mean S of the data decreases wth E c.m.. The eak of S dstrbuton shfts to lower value. Two models ( jet model and hase-sace model ) are comared wth data. The jet model agrees wth the data. The hase-sace model dsagrees wth the data. These are evdence for jet. The dstrbuton of the jet axs has deendence on azmuthal angle φ. Ths s another evdence for jet. Jet became later an mortant subject of QCD (quark-gluon hyscs ). 9
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ビームの偏極について シンクロトロン加速器にて加速された電子 陽電子ビームはシンクロトン放射をして徐々に偏極される (sokolov-terenov 効果 ) このとき陽電子は磁場と同じ向きに 電子は磁場とは反対向きに偏極される 今回の SLAC の実験ではビームの偏極度を P として e + B e- z P = 0.47 ± 0.05 という値となっている また対消滅により生成される仮想光子のスピンの z 成分は 0 つまりスピンの方向は貯蔵リング面内にあることがわかる 11
ジェット軸の角度分布 dσ dω 1+ α cos θ + P α sn θ cos ϕ α = σ T σ T σ L + σ L σ T : Transverse roducton cross secton σ L : Longtudnal roducton cross secton α = 0.78 ± 0.1 ジェット軸の角度分布 : d dω σ 1 + (0.78 ± 0.1) cos θ 1
仮想光子について 重心系 運動量保存則により光子の 4 元運動量は μ q = E ( c,0,0,0) つまり光子の不変質量が M E = c 0 e + E (, 1,0,0) c E (, 1,0,0) c e - となりゼロではなくなるので この光子は仮想光子であると考えられる 1
14 球形指数について = T 1 1 1 1 1 r r r この行列の固有値を得るために対角化させる k k Tu k u r r λ = (k=1,,) = + + = S mn 1 ) ( r λ λ λ λ λ は最小の固有値 かつ固有ベクトルにたいして垂直方向の運動量成分の 乗和を表す この λ の固有ベクトルがジェット軸と定義される