LHC能区相对论重离子碰撞中的双轻子产生及其信号与背景的研究_英文_

LHC能区相对论重离子碰撞中的双轻子产生及其信号与背景的研究_英文_ ()第 37 卷第 3 期V o .l 37 N o. 3 自然科学版 华中师范大学学报 ()2003 年 9 月 JOU RN A L O F C EN T RA L CH IN A N O RM A L U N IV ER S IT Y N a t. Sc .i Sep t. 2003 () A r t ic le ID : 1000- 1190 200303- 0310- 06 ƒStudy odf i leptonp rodu ciotn ansd ig na lbackgrou nexd trac iton in rela t iv ist ic heavy iino n te rac iotn s a t L HC 22, , , ZHO U D a icu iP EN G R u YA N G H o n g yan 22, D IN G H en g to n g X IA N G W en ch an g ( , ,In st itu te o f P a r t ic le P h y sic sCo llege o f P h y sica l Sc ience and T ech no lo gy ), 430079C en t ra l C h ina N o rm a l U n ive r sityW uh an λθ() ( ) A bstra c t: T h e p ro duc t io n o f H eavy2f lavo r qua rk c c and b b in pp co llisio n s is de sc r ibed unde r , 22PQ CD f ram ew o rk th e ex t rapo la t io n f rom h ad ro n h ad ro n up to nuc leu snuc leu s co llisio n s is ba sed o n . G laube r m o de l and tak ing in to acco un t nuc leu s sh adow ing effec tW e sim u la te th e h eavy qua rk p ro duc2 2. t io n and th e ir decay to lep to n in P b P b co llisio n a t L H CT h e m uo n ra te and th e inva r ian t m a ss sp ec2 . t rum o f d im uo n s h ave been p red ic ted in A L IC E fo rw a rd reg io nT h e de tec t io n effec t ana ly sis tech n ique ƒ. and signa lback g ro und ex t rac t io n o f m uo n p a ir s a re d iscu ssedT h e m ea su rem en t p rec isio n o f co r re la ted .m uo n p a ire s h a s been p red ic ted in A L IC E exp e r im en t : ; ; ; Key word sre la t iv ist ic h eavy io n co llisio nh eavy f lavo u r p ro duc t io nd ilep to n decayda ta ana ly sis ; tech no lo gyexp e r im en ta l de tec t ing effec t 414. 2; 341CL C n um ber: O O D ocum en t code: A 1 L a t t ice Q CD ca lcu la t io n sp red ic t th a t w h en en e r2 du c t io n co u ld h ave b een reach ed a t th e se den sity o r tem p e ra tu re a re su ff ic ien t ly h igh a n ew .g ie s , p h a se o f m a t te r co u ld app ea rth e p la sm a o f , im po r tan t to stu dy is E xp e r im en ta llyth e (). qu a rk s an d g luo n s Q GP T h is p h a se t ran sit io n , th e co n t in u um o f th e d im uo n p ro du c t io n o r ig i2 150 ,co u ld h app en a t tem p e ra tu re s a ro u n d M eV n a t in g m o st ly a t SP S en e rg ie s f rom u n co r re la ted co r re spo n d in g to an en e rgy den sity o f som e decay s o f p io n s o r k ao n s an d du e to a b ack g ro u n d 3. o f com b in a to r ia l p a ir sT h e re la t ive w e igh t o f th is ƒ.GeV fm Su ch ex t rem e co n d it io n s co u ld b e com b in a to r ia l b ack g ro u n d is in c rea sin g w ith th e reach ed in re la t iv ist ic h eavy io n co llisio n s a t , m a ss o f th e co llid in g sy stem an d w ith th e en e rgyƒƒ. C ERN SP S an d BN L R H ICT h e th eo ry p red ic t s m ak in g a m o re c r it ica l p ro b lem fo r th e m o st cen2 th a t th e re la t iv ist ic h eavy io n co llisio n s a t L H C , t ra l co llisio n s o f th e h eav ie st io n sw h e re th e 7 ,co u ld in du ce en e rgy den sity w ith 3 2 .Q GP p ro du c t io n is m o re lik e ly 27 ƒ.t ran sit io n to 2 GeV fm A n effec t o f th is , A t L H C en e rg ie sth e co n t in u um o f th e w a rd deco n f in ed m a t te r co u ld b e th e m e lt in g o f λ d im uo n p ro du c t io n o r ig in a t in g f rom d irec t qqan 2 . ra re h eavy qu a rk s re so n an ce sA n d m ea su rem en t ƒo f J 7 an d 4 p ro du c t io n is th en a p rom isin g w ay n ih ila t io n o r op en f lavo r p ro du c t io n w ill b e ve ry 3 . .im po r tan tT h is co n t in u um th en re su lt s f rom to o b ta in a sp ec if ic p ro b e o f deco n f in em en t , T h e se re so n an ce s can b e m ea su red th ro u gh th e ir sim ila r p ro du c t io n m ech an ism s to re so n an ce sb u t . is no t sen sit ive to deco n f in em en t an d co u ld th u s d im uo n decay ch an n e lIn d ica t io n s o f th e anom a2 se rve a s a refe ren ce in th e stu dy o f re so n an ce s ƒsupp re ssio n h a s b een o b se rved a t lo u s J 7 4 supp re ssio n. , SP S su gge st in g th a t th e th re sho ld o f Q GP p ro 2 206210.: 2003Rece ived da te (): . 10075022.Fun da t ion item T h is w o rk w a s suppo r ted by th e N a t io na l Sc ience Fo unda t io n o f C h ina unde r G ran t N O 22th ree se t s o f th e m o st up to da ta p a r to n d ist r ib u2 In th is w o rk w e w ill sta r t f rom a de sc r ip t io n 9 10 , 2′, 0t io n fu n c t io n sGRV H M R S D an d M R S 2, o f h a rd p ro ce sse s in p p co llisio n ex t rapo la te to 0′, 2D w h ich a re com p a t ib le w ith th e deep in e la st ic h eavy io n s th an k s to a g lo b a l m o de l an d tak e a lso , sca t te r in g da ta f rom H ERA in to th e N L O ca lcu2 in to acco u n t co llec t ive effec t s su ch a s sh adow in g λθ. la t io n s fo r th e p ro du c t io n s o f cc an d bbIn th e , o f st ru c tu re fu n c t io n sth en sim u la te th e p ro du c2 , fo llow in gre su lt s o f th e se ca lcu la t io n s w ill b e t io n an d decay p ro ce ss o f ch a rm ed an d bo t tom in u sed a s b a sis to ex t rapo la te f rom pp to A A co lli2 ra la t iv ist ic h eavy io n co llisio n s w h ich sho u ld ap 2 .sio n s . p ea r in a fo rw a rd m ea su rem en t a t L H CT h e ex 2 W e a ssum e th a t th e n u c leo n den sity in h eavy , p e r im en ta l de tec t io n effec t san a ly sis tech no lo gy 2n u c leu s is a th ree p a ram e te r W oo dSaxo n d ist r i2 o f da ta an d th e ex t rac t io n o f sign a l an d b ack 2 :b u t io n g ro u n d o f m uo n p a ir s a re d iscu ssed an d th e m ea2 2 su rem en t p rec isio n o f t ru e m uo n p a ir s is p red isc t2 ) ( rR 1 + ƒA ( ) ( ) Θ Θ r = 0, 2 A ( ) 1 + exp [ r - R ] A ƒz 0 .ed in A L IC E w h e re Θ0 is th e cen t ra l den sity w h ich is de te rm in ed 1 Hea vy f la vor produc t ion 3 ( )drΘr= A , z f rom no rm a liza t io n A 0 ? sec t io n fo r T h e h eavy qu a rk in c lu sive c ro ss () = 0. 54 fm th e su rface th ick n e ss an d th e n u c le2 13 ƒ- 1ƒ3 pp co llisio n s in p e r tu rb a t ive Q CD is o b ta in ed a s a R u s rad iu s A = 1. 19A -1. 61A . fmW e in 2 h ( ) ? co n vo lu t io n o f p a r to n den sity x , ΛF w ith f a i 11, 12 () T A B , t ro du ce th e n u c lea r o ve r lap fu n c t io n δb δ() h a rd sca t te r in g c ro ss sec t io n Ρi j s, m Q , ΛR .2 p ropo r t io n a l to th e n um b e r o f n u c leo n n u c leo npp h { 1()= dx dx f x , ΛΡQQ1 2 i 1 F ? :co llisio n s ? i, j? ? ? δδh 2 ()() () 1 × f , Λ, m , Λj i x 2 F Ρj sQ R ,() () ( ) =Θ Θ T b z , bz , b A B AB A AB B ? i j h e re an d a re th e in te rac t in g p a r to n s an d th e ? ? ? ? ? h ( ) ()× t b - bA - bB d bA d bB dz A dz B , 3 f fu n c t io n s i a re th e den sit ie s o f qu a rk s, an t i2 ΘΘw h e re A an d B a re th e no rm a lized den sity d ist r i2 qu a rk s an d g luo n s eva lu a ted a t m om en tum f rac2 δb u t io n s fo r th e n u c le i A an d B w ith th e sp a t ia l co 2 t io n x an d fac to r iza t io n sca le ΛF . Ρi j is ca lcu lab le ? ? () ΑΛ a s a p e r tu rb a t io n se r ie s in s R w h e re th e st ro n gb, z b, z o rd in a te s A A an d B B th e po sit io n vec to r s w ith co up lin g co n stan t is eva lu a ted a t th e reno rm a liza2 re sp ec t to th e cen te r o f n u c le i A an d B re sp ec t ive2 δ δ Λ, s= x x s, w ith st io n sca le R an d 1 2 th e squ a re o f . lyD u e to th e in dep en den ce o f th e n u c leo n s in s th e p a r to n ic cen te r o f m a ss en e rgy an d th e :th is m o de l com e s ? ? squ a re o f th e cen te r o f m a ss en e rgy o f th e co llid2 ( ) ( ) 4 T A B b d b = A B .? () Λ, in g h ad ro n s h 1 an d h 2. FA t lead in g o rde r L O 2 Y an p ro du c t io nH a rd p ro ce sse s su ch a s D re ll= Λ= Λ Λ =2m . 2R w h e re c A t th e low e sto rde r 2 λ {o f co n t in u um h igh m a sse s d im uo n s o r p ro du c t io n () O Α, 22? s tw o to tw o Q CD su bp ro ce sse s qqQ Q o f op en h eavy f lavo r s seem to h ave a ra te fo llow 2 { 22 . ? to a re co n side redA t th e N ex tan d gg Q Q13, 14 3 2. in g th e n um b e r o f n n co llisio n s O n e th en() () O Α,N L O s su bp ro ce sse s in 2 L ead in g o rde r 50% exp ec t o f th e c ro ss sec t io n to o ccu r in th e λ λ { { ) ( ? ? ?, ,qc lu de qqQ Qggg Q Qgan d q g 10% m o re cen t ra l even t s du e to th e sh ap e o f { λ(). 2Q Qq qT h e qu a rk g luo n g rap h s h ave b een in 2 ?11, 12 ( ) 2 T h e m u lt ip lic ity fo r th e h a rd p ro T b . te rp re ted a t Bo rn leve l a s th e sca t te r in g o f a h eavy A B qu a rk ex c ited f rom th e n u c leo n sea w ith a ligh t ce sse s is th en exp ec ted to b e in c rea sed b y a fac to r c. c. qu a rk o r g luo n an d a re refe r red to a s f lavo r ex c i2 f ,5 w ith re sp ec t to th e o n e ave raged o n a ll . ta t io nH eavy qu a rk p ro du c t io n b y g luo n fu sio n im p ac t p a ram e te r s. { ?. dom in a te s th e pp Q QX p ro du c t io nT h e ca lcu la2 T h is in c rea se o f th e m u lt ip lic ity du e to sup e r2 3(O Α) t io n s o f th e in c lu sive c ro ss sec t io n va lid to 2s po sit io n o f n n co llisio n s is n eve r th e le ss lim ited 5 , 8 . . 5 h ave b een p e rfo rm ed R efin t ro du ce b y a co llec t ive effec t ca lled n u c lea r sh adow 2 ()华中师范大学学报 自然科学版 第 37 卷312 15, 16 w h ich is a de st ru c t ive in te rfe ren ce d im in2 in g te r iza t io n w ith A dep en den ce, a ssum in g sim ila r to qu a rk s, an t iqu a rk s an d g luo n s ish in g th e f lu x an d in te rac t io n s o f p a r to n s in re2 x. g io n o f low W e co n side r th e fo llow in g p a ram e2 () f x a A ƒ() S A x =) ( A f xaN ƒ 2 1ƒ3 () 1. 08 - 1 x A 163 2 ƒ()) - (Α- , 5 = 1 + 1. 19 ln A [ x - 1. 5 x + x x + 3x x x -exp A0 L 0 L x 2 ()x ln A + 1 0 13 ƒ() Α= 0. 1 A - 1, x = 0. 1 x = 0. 7. w h e re A 0 an d L 2, 4 10 In o u r rap id ity w in dow fo r GeV m a ss a t x L H C en e rg ie s w h ich co r re spo n d s to T o f th e o rde r - 4- 5 10, 10, S 50%. o f A is o n th e leve l o f W e de2 AA{ { ΡQQ du ce th e c ro ss sec t io n p ro du c t io n fo r Q Qp a ir s 2A in a n u c leu sn u c leu s o f m a ss co llisio n f rom th epp{Ρpp o n e QQ b y: AA 2 pp { { Ρ= S A ΡQQA QQ an d th e co r re spo n d in g m u lt ip lic ity: AA c. c. c. c. AA AA { { M = f ΡƒΡ, QQQQIN T AAΡw h e re IN T is th e in te rac t io n c ro ss sec t io n fo r th e If w e a ssum e th a t th e fo rw a rd A A co llisio n. pp pp λθΡ=Ρ=h em isp h e re cc 1. 07 b a rn , bb 0. 085 m b a rn λ. 1 F igA verage m uon ra te per even t f rom cc fo r th e to ta l p ro du c t io n c ro ss b a sed upo n R ef. 5 AA λ λθan d bba s a f un c t ion of a tran sver sa l Ρ=sec t io n o f cc an d bb in pp co llisio n an d 5. 54 IN T m inPbPbc. c.PbPbc. c. m om en tum P thre sho ld f orT λθM = 21. 7 M = b a rn w e o b ta in an d cc bb - 5. 5 PbPb co ll is ion s a t TeV 1. 64. qu a rk s in to h ad ro n s is tak en in to acco u n t th ro u gh 2 L ep ton ic deca y an d in va r ia l m a ss 18: th e fo llow in g p a ram e te r iza t io n spec trum - 2 1 ΕQ - 1 () ()7 , D z ? z 1 - - H ƒQ 1 - z z 2 W e now b u ild exp e r im en ta llik e m uo n even t s z = p p , ƒH Q th e f rac t io n o f h eavy qu a rk m o 2 w h e re an d stu dy how th ey w ill app ea r in th e da ta an a ly2 Ε, m en tum ca r r ied b y th e f in a l sta te h ad ro n an d Q . sisW e a ssum e th a t th e p ro b ab ility o f p ro du c in g 2 2 ? m q ƒm Q , . , 2 ieth e ra t io o f th e effec t ive ligh tan dλ N qu a rk p a ir s qqin A A co llisio n s fo llow s a Po isso n 2.h eavyqu a rk m a sse s law N λT h e m uo n is th en dedu ced u sin g a th ree bo d2 qq u - u λ() () 6 e,p N qq, u =λN qq?+ + ?ie s sem ilep to n ic decay a lo n g b ΛΜc an d cΛu + + . h e re is th e ave rage va lu e o f h eavy qu a rk p a ir s ΜsT h e in c lu sive b ran ch in g ra t io fo r D m e2 λ() B R D ? ΛX , 14? . , so n decay to lep to n is T h e . p rev io u sly o b ta in edH eavy qu a rk p a ir s fo r cc an d () B R B ? ΛX ,b ran ch in g ra t io fo r B m e so n s is θbb a re gen e ra ted w ith th e m a ss d ist r ib u t io n 19 5 2adap ted f rom w h ich u se s M R S D ’ st ru c tu re 10? .T h e decay s ca lcu la ted in th e qu a rk s re st . fu n c t io n sT h e t ran sve r sa l m om en tum d ist r ib u2 f ram e a re boo sted b ack to th e labo ra to ry, th en + - ΛΛ+ - + - t io n s a re def in ed u sin g th e p a ram e te r iza t io n f rom M , y P .ΛΛΛΛan d T a re dedu ced 17 , CD F exp e r im en ta l da ta an d rap id ity d ist r ib u2 T h e de tec t io n o f th is m uo n s b y a sp ec t rom e2 t io n s a re co n side red to b e f la t w ith a Gau ssian ta il te r o f th e k in d fo re seen fo r A L IC E h a s b een sim u2 λ20 , 244 o f w id th u n ity cen te red re sp ec t ive ly a t fo r ccb y co n side r in g a fo rw a rd p seu do rap id i2 la ted θ 3 . an d fo r bb T h e f ragm en ta t io n o f c an d bty dom a in 2. 4 < Γ < 4 an d b y tak in g in to acco u n t th e m u lt ip le sca t te r in g an d en e rgy lo ss in th e ab 2 .so rb e r an d th e re so lu t io n o f th e t rack in g sy stem . 1 T h e F igshow n s th e even t ra te o f m uo n p ro du c2 2t io n f rom ch a rm an d bo t tom decay s o n P b P b co l2 5. 5 , lisio n s a t T eV a s a fu n c t io n o f th e t ran sve r2 m in P ,sa l m om en tum th re sho ld T in fo rw a rd reg io n. λ 3 ƒ, B e low GeV cth e co n t r ib u t io n s f rom cc decay s m in , P a re p redom in an tth en a s T in c rea se s th e decay s θ . f rom bb b ecom e dom in an tT h e g lo b a l com b in a to 2 r ia l m a ss sp ec t rum o f d im uo n p ro du c t io n is show n θ( ) . 2 so lid lin e T h e co n t r ib u t io n s f rom bbin F ig. λθλ an d cc in c lu de no t o n ly decay s f rom t ru e bb o r ccF ig. 3 Com par ison be tween the d istr ibut ion s λp a ir s, b u t a lso com b in a t io n s b e tw een qu a rk s an d f or the corre la ted m uon pa ir s f rom cc - 5. 5 decay f or PbPb co ll is ion s a t TeV an t iqu a rk s o f sam e f lavo r b u t o r ig in a t in g f rom . d iffe ren t p a ir sG iven th e ve ry h igh n um b e r o f p a ir s p ro du ced in th e se co llisio n s th is com b in a to 2 r ia l p h enom eno n b ecom e s th e m a in so u rce o f th e . m a ss co n t in u um o f m ea su red p a irW e can see th a t th e co n t r ib u t io n s f rom op en ch a rm a re im 2 + - M < 8 ƒ0 < . po r tan t in th e reg io n ΛΛGeV cT h ey w ill a lso b e m ix ed w ith th e m uo n s com in g f rom , o th e r so u rce sp a r t icu la r ly fo r th e low m a ss p a r t . w ith Πan d K decay s no t p re sen ted h e reIn su ch a w ay it w ill b e im po ssib le to d isen tan g le th em o n a . p u re ly exp e r im en ta l b a sisW h en en te r in g h igh e r θ m a ss reg io n , th e d im uo n p ro du c t io n f rom bb de2 F ig. 4 Com par ison be tween the d istr ibut ion s λ.cay b ecom e s p redom in an t f or the corre la ted m uon pa ir s f rom bb - 5. 5 A n even m o re in te re st in g o b se rva t io n h a s decay f or PbPb co ll is ion s a t TeV b een m ade w h en com p a r in g th e m a ss sp ec t rum o f { ( m uo n p a ir s o r ig in a t in g f rom o n e Q Qp a ir t ru e ) p a irw ith th e o n e co n ta in in g a lso th e com b in a to 2 . 3 r ia l p a ir s f rom d iffe ren t qu a rk p a ir sT h e f igu re is th e ra t io o f m ix ed m uo n p a ir s to th e co r re la ted λθ4 , m uo n p a ir s fo r cc an d th e f igu re fo r bb w h ich show s th a t th e la st com po n en t is van ish in g fo r , h igh m a sse san d it th en f in a lly app ea r s f ree o f , com b in a to r ia l com p lica t io n sd irec t ly com p a rab le to th e sam e p ro du c t io n in pp an d A A co llisio n s . an d to th e 4 p ro du c t io nIn deed th e p ro b ab ility to b u ild a com b in a to r ia l p a ir is n eg lig ib le fo r h igh t ran sve r se m om en tum m uo n s w ho se m u lt ip lic ity λλ . 2 F igD im uon in var ian t spec trum f rom cc an d bb( ) 3 4 f igu re an d is o rde r o f m agn itu de sm a lle r - decay s an d the ir com b ina t ion s in PbPb 2 2.th an th e p ro b ab ility o f can d b decay in to m uo n 5. 5 co ll is ion s w ith TeV a t L HC 1 T h is h a s a lso b een ve r if ied in a sim p lif ied d i2 ()华中师范大学学报 自然科学版 第 37 卷314 + + ) ()(m en sio n a l sim u la t io n w ith tw o p a ram e te r s rep ro 2 Co v N , N ? 16 0. 2 expo n en t ia l slop e an d dedu c in g th e m a in t ren d s: W e o b ta in + - 21, 24 + + - - 〈N .cay p ro b ab ility ()17 〉? 2 〈N 〉〈N 〉, B ack w h ich is su itab le to th e com b in a t io n o f m uo n s 3 ƒs igna lba ckgroun d Ex tra c t ion of , , f rom Πk u n co ree la ted decay an d d iffe ren t an d m ea surem en t prec is ion .so u rce s + - 〈N 〉〈N 〉If th e d ist r ib u t io n s o fan da re T h e re a re seve ra l so u rce s to p ro du ce d im uo n s + - N = N = N , ,w e h ave N = t rue2p a ir symm e t ry , in A L IC E exp e r im en tw h ich can b e d iv ided in to + - + + 〈N. . , ie 〉 = 〈N 〉. , 〈N 〉 ? T h e refo re: th e fo llow in g th ree c la sse st ru e m uo n p a ir s - - 〈N 〉. It is ea sy to ge t , 22 , ƒw h ich decay f rom J 7 4 an d D re llY an p seu do + + + 2 ( ) ()18 〈N 〉= 〈N 〉- 〈N 〉2, ƒt ru e m uo n p a ir s du e to th e u n co r re la ted p a ir s + - 2 ()〈N 〉= 〈N 〉.19 w h ich decay f rom co r re la ted h eavy qu a rk p a ir s T h e t ru e p a ir s an d com b in a to r ia l p a ir s can b e 2, an d p seu do com b in a to r ia l p a ir san d p e rfec t ly u n 2 ,o b ta in ed b y fo llow in g , . co r re la ted p a ir s f rom p io n k ao n decayE xp e r i2 + - + + - - + - ( )〈N R ecom b 〉- 〈N 〉+ 〈N 〉 ,, m en ta llyth e d ist r ib u t io n s o f p a ir s w ith ΛΛ - - + + ()20 = 〈N 〉?〈N T ru e 〉, . an d ΛΛcan b e m ea su redO n ce th e m ean ΛΛ+ + - - + - ()21 〈N 〉+ 〈N 〉? N B ack. 〈n 〉va lu eΛo f m uo n s is g iven b y exp e r im en t an d if ( ) ( ) ( )17, 20 In equ a t io n s 21 th a t th e an d m ean, it is a Po isso n ian d ist r ib u t io n th e n um b e r o f 2 th ro u gh sign a l an d b ack g ro u n d can b e de r ived 〈n 〉2. ƒΛ com b in a to r ia l p a ir s is p ropo r t io n a l to 2.lik esign p a ir s Co n side r th e p a r t ic le p ro du c t io n o f sin ge + - B y th e abo ve w ay s, w e ex t rac t th e t ru e p a ir s N ,. N ven tA ssum in g deno te re sp ec t ive ly th e an d b ack g ro u n d o f th e sim u la ted sam p le in A L 2 p a r t ic le n um b e r w ith po sit ive an d n ega t ive . IC E d im uo n de tec to rT h e refo re th e m ea su rem en t , 2 2ch a rgeth e lik ean d u n lik esign p a ir s can b e .p rec isio n o f sign a l can b e dec ided b y th e m e tho d ,com po sed o f th em a s fo llow in g + 2 + + + + + 5 6 T h e f igu re s an d a re th e m ea su rem en t p rec isio n ) ) ((()N - 1= 2N N N - N , 8 = λθ- 2 - - - - - , . w ith ccbbT h e an a ly sis m e tho d can a r r ive to ) () () (1= N - 2N N N , 9= N - + - + - , th e m ea su r in g accu racy o f seve ra l p e rcen tw h ich ()= N N . 10 N p ro v ide s an eno u gh effec t ly m e tho d to A L IC E U sin g th e abo ve re la t io n sh ip o f sin g le even t, w e m ea su rem en t in su ch a com p lica ted m uo n p ro du c2 can b u ild th e m ean va lu e o f even t sam p le w ith .t io n 2 2. ex am in e lik ean d u n lik esign p a ir sW e n eed to ,th e fo llow in g va r iab le s + + + + () 2〈N 〉=〈N N - 1〉 + 2 + () 11 =〈N 〉- 〈N 〉, - - - - ) ( 2〈N 〉=〈N N - 1〉 - 2 - ()=〈N 〉- 〈N 〉, 12 an d + + + 2 + ( 〈N 〉= 〈N 〉- 〈N 〉 + ) ) (()+ V a r N ƒ2, 13 + - + - 〈N 〉=〈N 〉〈N 〉 + - )()(+ V a r N , N . 14 -+ , N N If th e d ist r ib u t io n s o f a re th e Po isso n ian + - F ig. 5 M ea surem n t prec is ion of s igna l an d N N , ,typ e an d an d decay in dep en d lyth e refo re λ+ + backgroun d f or d im uon f rom cc decay ) (()15 V a r N - 〈N 〉? 0, - 5. 5 f or PbPb co ll is ion s a t TeV an d Ref eren ce s: 1 M a t su i T. Q ua rk m a t te r ’97: th eo re t ica l o ve rv iew [ J . N uc l , 1998, 638: 19, 33.P h y sA cc 2 . [ . A L IC E Co llabo ra t io nA L IC E tech n ica l p ropo sa l M 271, ƒ95ƒ3.C ERN L H CC L H CC p , . ƒ2M a t su i T Sa ta HJ 7 supp re ssio n by qua rk g luo n p la sm a 3 [. , 1986, 178: 416, 422.fo rm a t io n J P h y s L e t tB , , . 2ƒA b reu M C A le ssand ro B A lexa CJ 7 and D re llYan 4 2ƒ158 c ro ss sec t io n in P bP b in te rac t io n s a t GeV c p e r nuc leo n [. , 1997, 410: 327, 336.J P h y s L e t tB , , , . Gava i R Kh a rzeev D Sa tz H e t a lQ ua rko n ium p ro duc t io n 5 [. , 1995, 10: 3 043in h ad ro n ic co llisio n s J In t J M o d P h y sA , 3 054. , , . N a sso n P D aw so n SE llis P KT h e to ta l c ro ss sec t io n fo r 6 F ig. 6 M ea surem n t prec is ion of s igna l an d [ .th e p ro duc t io n o f h eavy qua rk s in h ad ro n ic co llisio n s J λ backgroun d f or d im uon f rom bbdecay N uc l P h y s, 1988, B303: 607, 633. - 5. 5 f or PbPb co ll is ion s a t TeV N a sso n P , D aw so n S, E llis P K. T h e o ne p a r t ic le inc lu sive 7 d iffe ren t ia l c ro ss sec t io n fo r h eavy qua rk p ro duc t io n in h ad ro n ic co llisio n s [J . N uc l P h y s, 1989, B327: 49, 92. In summ a ry, d im uo n f rom ch a rm an d b eau ty , . 2B e rge r E L M eng RH eavyqua rk c ro ss sec t io n s a t h ad ro n 8 2decay w ill b e h igh ly p ro du ced in P b P b co llisio n s [. , 1992, 46: 169, 180.co llide r ene rg ie s J P h y s R evD β. a t L H C en e rg ie s T h e se im po r tan t so u rce s o f G luck M , R eya E , V o g t A. P a r to n d ist r ibu t io n s fo r h igh en29 , 134.[. , 1992, 53: 127e rgy co llisio n s J Z P h y sCd im uo n co n t in u um m igh t b e an idea l refe ren ce fo r , , . M a r t in A D S t ir ling W J Ro bbe r t s R GP a r to n d ist rbu2 th e stu d ie s o f th e supp re ssio n o f re so n an ce s b y 10 , 150.[ . , 1993, 306: 145t io n s up da ted J P h y s L e t tB. th e deco n f in ed m ed iumU n fo r tu n a te ly th is in 2 . 2W o ng C YIn it ia l ene rgy den sity o f qua rk g luo n p la sm a in 11 c rea se o f th e n um b e r o f h eavy qu a rk s p a ir s c rea te s 2[ . , 1984, 30:re la t iv ist ic h eavyio n co llisio n s J P h y s R evD a lso in th e an a ly sis p ro ce ss a b ack g ro u n d o f com 2 961, 971. . b in a to r ia l p a ir sT h is b ack g ro u n d is im po r tan t in . 2W o ng C YB a ryo n d ist r ibu t io n in re la t iv ist ic h eavyio n co l2 12 , 984.[. , 1984, 30: 972lisio n s J P h y s R evD , th e in te rm ed ia te m a ss dom a in b e low th e 4 b u t . ƒKh a rzeev DT h eo re t ica l in te rp re ta t io n s o f J 7 supp re s2 13 th e d im uo n co n t in u um abo ve o r ig in a te s m a in ly ,: [ . , 1998, 638: 279sio nA summ a ry J N uc l P h y sA c. f rom th e co r re la ted p a ir sT h e h igh m a ss p a r t o f 290.c th e co n t in u um co u ld th en p ro v ide a d irec t p ropo r2 , , . ƒA b reu M C A le ssand ro B A lexa CA nom a lo u s J 7 sup 2 14 t io n a l m ea su rem en t o f th e op en h eavy f lavo r s p ro 2 2158 ƒp re ssio n in P bP b in te rac t io n s a t GeV c p e r nuc leo n [. , 1997, 410: 337, 343J P h y s L e t tB du c t io n an d th u s po ssib ly se rve d irec t ly a s a refe r2 θ, , , . Em e lyano v V Kho d ino v A K le in S R e t a lIm p ac t P a2 15 en ce fo r h a rd p ro ce sse s. In th is co n t in u um th e bb 2ƒram e te r D ep endence o f J 7 and D re llYan p ro duc t io n in , com po n en t sho u ld b edom in an tm ak in g it a b e t te r . h eavy io n co llisio n s a t s= 17. 3 GeV [ EB OL . h t tp: ƒƒƒrefe ren ce fo r th e 4 supp re ssio n stu dyT h e ex 2 NN a rx iv. o rgƒP Scach eƒh ep 2p h ƒp dfƒ9809ƒ9809222. p df.— ƒt rac t io n o f sign a lb ack g ro u n d is d iscu ssed an d th e 16 , . : W ang X N Gyu la ssy M H IJ IN GA M o n te C a r lo m o de l m ea su rem en t p rec isio n o f co r re la ted m uo n p a ir s , [ .fo r m u lt ip le je t p ro duc t io n in pp pA and A A co llisio n s J , h a s b een p red ic tedw h ich app ea r s an eno u gh h igh P h y s R ev, 1991, D 44: 3 501, 3 516. m ea su r in g p rec isio n w ith t ru e m uo n p a ir s b y o u r 17 (), , , .A be F A k im o to H A kop ian A e t a l CD F Co llabo ra t io n θ an a lyzin g m e tho d s in A L IC E exp e r im en t. ƒP ro duc t io n o f J 7 m e so n s f rom ς c m e so n decay s in ppco lli2 sio n s a t s = 1. 8 T eV [ J . P h y s R ev L e t t, 1997, 79: 578, 583.T h e au tho r s lik e to A ckn owlegem en t: , , , . 18 P e te r so n C Sch la t te r D Schm it t Ie t a lSca ling v io la2 th an k P ro fe sso r D en is Jo u an , P ro fe sso r J u rgen + - [ . ,t io n s in inc lu sive eeann ih ila t io n sp ec t ra J P h y s R ev , Sch u k raf tth e co lleagu e s o f d im uo n g ro up s o f 1983, 27: 105, 111.D IPN a t O r say an d o f A L IC E co llabo ra t io n fo r .va lu ab le d iscu ssio n s ()下转第 329 页 第 3 期王恩科: 喷注淬火的细致平衡效应 329 8 B raa ten E , P isa r sk i R D. So f t am p litude s in ho t gauge: A [. , 1990, 337: 569, 580.gene ra l ana ly sis J N uc l P h y sB 喷 注 淬 火 的 细 致 平 衡 效 应 0王 恩 科 () 华中师范大学 物理科学与技术学院 粒子物理研究所, 武汉 430079 摘 要: 讨论了高能部分子穿过夸克胶子等离子体时热胶子的细致平衡效应. 在热介质中, 受激的热 胶子发射降低部分子的能量, 而热吸收增加部分子的能量, 其净贡献导致部分子能量损失的减少. 部分 子能量损失的相对减少对中等能量的喷注是重要的, 而对非常高能量的喷注可以忽略不计. 修正后的能 量损失对能量的依赖性将影响中等 p 强子谱压低的形状.T 关键词: 喷注淬火; 能量损失; 细致平衡; 夸克胶子等离子体; 热介质 ()上接第 315 页 19 ( ), . w o rk shop o n new p h enom ena in h igh ene rgy exp e r im en t s M o n tane t L G ie se lm ann A P a r t ic le da ta g ro up R ev iew [ . : ,, C W uh anP re ss o f C en t ra l C h ina N o rm a l U n ive r sity o f p a r t ic le p rop e r t ie s [ J . P h y s R ev, 1994, D 50: 1 173 1997, 140, 157.1 814. 20 , . 23 Jo uan D , Zho u D C. S tud ie s fo r d im uo n m ea su rem en t in th e Zho u D C Jo uan DS tudy o f com b ina to r ia l back g ro und o f [ . , [. ƒd im uo n p ro duc t io n in A L IC E J A L IC E in te rna l repo r tfo rw a rd reg io n in A L IC E M A L IC E in te rna l no te PH Y , 1999203209.95204, 15 1995.C ERN M a rch , . , . , , Zho u D C Jo uan DE x t rac t io n o f signa l and back g ro und 21 24 Zho u D C Jo uan DO n iaop en h eavy f lavo u r sm e so n de2 [. , ,fo r d im uo n s in A L IEC J A L IC E in te rna l repo r tC ERN cay and com b ina to r ia l effec t s in m uo n p a ir s m ea su rem en t s 15 M a rch , 2000203215. [. 296224.in A L IC E a t RH IC M IPN O D R E 22 Zho u D C . Som e recen t re su lt f rom EM U 01 exp e r im en t [. , . A L iu F engH u Y ianP ro ceed ing s fo r in te rna t io na l 能区相对论重离子碰撞中的双轻子产生及其信号与背景的研究L HC 0 0 , 杨红艳, 丁亨通, 向文昌茹周代翠, 彭 ()华中师范大学 物理科学与技术学院 粒子物理研究所, 武汉 430079 λθ() 摘 要: 在微扰 框架下, 描述了强子2强子 2作用中重夸克 和 的产生; 基于 模 Q CD p p cc bb G laube r (() ) 型, 考虑核遮蔽效应, 推广强子2强子相互作用到核2核 2情况. 模拟了 能区铅2铅 2碰撞 A A L H C P b P b 中重夸克产生和轻子衰变, 预言了 向前区域的 , 讨论了 子产生率和双 不变质量谱子产物 A L IC E Λ Λ Λ 的实验观察效应; 建议了一种进行数据分析、抽出 子对信号和背景产物的物理, 预言了 实 Λ A L IC E 验中关联 , 解决了 实验中复杂 .子对的测量精度子产物的分离技术Λ A L IC E Λ 关键词: 相对论重离子碰撞; 重味产生; 双轻子衰变; 数据分析技术; 实验探测效应 () 作者简介: 0 王恩科 1963- , 男, 湖北公安人, 教授, 博士, 博士生导师, 主要从事高能核物理理论研究. () 0 0 周代翠 1951- , 男, 湖北枝江人, 教授, 博士, 博士生导师, 主要从事相对论重离子碰撞研究.