CDF Run II Status and prospects

Transcription

1 CF Run II Statu and propect C. Pagliarone INFN-Pia, V. Livornee 191, 561 Pia, Italy (On the behalf of the CF Collaboration) Abtract Run II at the evatron Collider tarted at the beginning of March 1. With extenive upgrade on both detector and electronic the CF II began to collect data. hi paper review early Run II phyic reult obtained by analyzing data collected before the middle of june. At the preent the undertanding of the detector performance i rather high o many analyi are already underway. 1. Run II evatron upgrade he Fermilab evatron Collider ha undergone, in the pat few year, a whole erie of upgrade to increae the intantaneou luminoity and to improve the collider bunch tructure. uring the firt phae of the Run II (Run IIA) the machine i expected to deliver to each of the two collider experiment: CF and, a goal luminoity of up to cm -1 with a center of ma energy of ev that i a bit larger than the 1.8 ev of the Run I. uring the preent Run IIA the evatron i operating much like in the previou Run IB with a higher integrated luminoity motly coming from an increae in the number of bunche and lightly higher proton and antiproton bunch intenitie. he planned integrated luminoity expected by the end of Run IIA i fixed to fb. he bunch tructure of the evatron Collider have been changed. Indeed, we paed from the 6 6 proton-antiproton bunche of the Run I to the preent he replacement of the Main Ring with the Main Injector a the injection ource for the evatron collider, leaded to an increaed number of proton per tore and at the ame time eliminated a ource of background for the detector. Several upgrade alo increaed the number of antiproton per tore. New Main Injector create antiproton beam with higher intenity and energy than in the Run I. In addition, the plan i to recycle 'unued' antiproton at the end of a collider tore rather than dump them. When the Recycler will be fully operational we expect to reach intantaneou luminoity up to 1 3 cm -1.

2 Sil icon tracking CMX IMU b) CMX Mini kirt CO CMP a) c) FIG. 1. a) 3-imenional view of the CF II detector configuration; the cutaway view of half ection of the inner portion of the CF II detector how the inner tracking region urrounded by olenoid, endcap calorimeter and, in the mot external part, by the muon ytem (CMP, CMX and IMU); b) view of the SVX detector; c) view of ISL detector.. he CF II etector Improvement Both evatron Collider etector have been improved in order to operate with the new machine performance that mean mainly with an increaed intantaneou luminoity a well a the critical bunch pacing tructure. In addition, there have been everal upgrade to increae the enitivity of the detector to pecific phyic tak uch a heavy flavor phyic, Higg boon earche and many other. A detailed decription of the CF detector upgrade may be found in the following document [1], []. Figure 1.a how a 3 cutaway view of the final configuration of the CF II experiment. he central tracking volume of the CF II experiment ha been replaced entirely with new detector, the central calorimeter ha not been changed, the muon ytem ha been mainly increaed in coverage. hee upgrade can be ummarized a follow: 1. Silicon tracking ytem done of 3 different tracking detector ubytem: Layer i a layer of ilicon detector intalled directly on the beam pipe to increae impact parameter reolution.

3 L (pb -1 ) Integrated Luminoity Jun Aug Sep Oct Nov ec Jan Feb Mar May Jun delivered on tape L1 Storage Pipeline: 4 Clock Cycle eep L Buffer: 4 Event ataflow of CF "eadtimele" rigger and AQ etector 7.6 MHz Croing rate 13 n clock cycle Level1: L1 7.6 MHz Synch. pipeline rigger 5544n latency <5 khz Accept rate L1 Accept Level : L Aynch. tage pipeline rigger ~ µ latency L Accept 3 Hz Accept Rate AQ Buffer L1L rejection:,:1 Store Number a) b) L3 Farm Ma Storage FIG. a) evatron Run IIA integrated luminoity hitory through June ; b) iagram of the CF II trigger architecture. Silicon Vertex etector (SVX II): in order to meet new phyic goal, a central vertexing portion of the detector called SVX II wa deigned (ee fig. 1.b). It conit of doubleided ilicon enor with a combination of both 9-degree and mall-angle tereo layer. he SVX II i nearly twice a long a the original SVX and SVX (96 cm intead of 51 cm), which were contrained to fit within a previou ga-baed track detector (VX), ued to locate the poition of interaction along the beam line. SVX II ha 5 layer intead of 4 of the two previou ilicon vertex detector and it i able to give 3-dimenional information on the track. Intermediate Silicon Layer (ISL) i a large radiu ( R Min =. 6 cm, R Max = 9. cm ) ilicon tracker with a total active area of 3.5 m. It i compoed of 96 baic unit, called ladder, made of three ilicon enor bonded together in order to form one electric unit. Figure 1.c give a chematic repreentation of the ISL detector. It i located between the Silicon Vertex etector and the Central Outer Chamber. Being at a ditance of.6 9. cm in the central part, from the beam-line, it cover a peudo-rapidity region up to η <.. Central Outer racker (CO): that i the new CF II central tracking chamber. It i an open cell drift chamber able to operate at a beam croing time of 13 n with a maximum drift time of 1 n. he CO conit of 96 layer arranged in four axial and four tereo uperlayer. It alo provide de / dx information for particle identification. 3. ime-of-flight etector (OF): New cintillator baed ime-of-flight detector ha been added uing the mall pace available between the CO and the olenoid. With 11 p time-of-flight reolution, the OF ytem enhance the capability to tag charged kaon in the P range from. 6 to few GeV / c a requeted from the B phyic earche underway. Figure 3.a and 3.b how the OF particle I reolution a function of particle

4 a) b) track OF c) d) FIG 3. a) and b) Expected OF particle I reolution a function of the particle momentum for low P particle; c) Φ(1) ignal recontructed with low momentum ( P < 1.5 GeV / c ) kaon; d) the ame a in c) after the OF information have been ued. momentum. Figure 3.c and 3.d demontrate how ignificantly change ignal and background eparation by adding OF information in the Φ(1) recontruction. 4. Plug Calorimeter: A new cintillating tile plug calorimeter ha been realized in order to have a good electron identification up to a peudorapidity range of η <. 5. Muon ytem ha alo been upgraded. he coverage in the central region ha been almot doubled compared to Run I ituation. And a new forward detector, the (IMU) have been added. 6. rigger he CF II trigger i organized in 3 different level. he Level 1 trigger (L1) i a dead-timele trigger with a 4 tage pipeline and can make a trigger deciion every 13 n with a total latency time of 5544 n. A new online proceor recontruct CO track (extremely Fat racker). L trigger add information within µ, to the object found by L1 trigger (electromagnetic or hadronic part of the calorimeter, miing tranvere energy, tub in the muon ytem). 7. ata Acquiition Sytem (AQ)} ha been adapted to hort bunch pacing of 13 n. It i capable to record data with event ize of the order of 5 KB and permanent logging of MB/.

5 a) b) FIG 4. a) Run II recontructed J / ψ and Ψ() event elected by uing the dimuon trigger; b) cτ ditance for the J/Ψ ample. 3. RUN II Early Phyic Reult 3.1 B Phyic B phyic i an extraordinary laboratory to tet everal fundamental apect of the Standard Model (SM). uring the Run I, , 11 pb -1 of data had been collected and ued to perform important B phyic meaurement [3] including the firt in( β ) meaurement on unitary triangle. he evatron collider, a mater of fact, i an excellent place for B phyic tudie both becaue it i poible to produce the full pectrum of meon and baryon with b quark, and alo becaue the b hadron production cro ection i large (compare 1 mb with few nb of e e - collider). Many of the decribed detector upgrade have been done indeed with a large emphai on heavy quark phyic (c, b, t). CF Run II phyic program can be yntheized a follow. CP violation meaurement uing mode uch a B J / ψk, B ππ, B KK and B K, B Mixing, earche for rare B decay, meaurement of lifetime, mae and branching ratio. At preent, the B phyic program i going through the refining of trigger trategie and performing variou high rate meaurement. Later on, we plan to meaure the in( β ) along with a meaurement of flavour ocillation by fully recontructing decay ( B π and B π π π with recontructed a φπ, B *, K K ) and then, after more than 3 pb will be available, the tudy K K of rare decay, together with the refining of the previouly performed meaurement, will take over. Preliminary CF Run II reult are hown in Fig. 5 and in able I. B

6 B d B c) Bu a) b) FIG. 5. Candidate invariant ma for a) ± K ± ± ± B u J / ψ ; b) B J / ψk ; c) B J /ψφ. rigger Strategie he total cro ection for light quark production i 3 order of magnitude larger than b-quark production. B hadron are then elected by uing three general trigger trategie: 1. Hadronic rigger;. Lepton plu diplaced track rigger; 3. i-lepton rigger: he firt trigger trategy take advantage of the long B hadron lifetime to dicriminate fully hadronic B decay from background. For the Run II CF have been equipped with a Secondary Vertex rigger (SV) that elect event that pa at Level 1 the looe requet of having two track with P trk > GeV / c in the event and, at Level, a diplaced vertex, earched by requiring a large impact parameter: > 1µm. hi trigger i extremely ueful a it i able to elect both rare two body decay uch a: B ππ (KK), relevant for CP violation meaurement, a well a hadronic B ± decay. he lepton plu diplaced track trigger i a trigger that elect event containing electron or muon with P trk > 4 GeV / c with the further requet of an additional track with large impact parameter. i-lepton rigger look µ for the preence of two oppoite ign muon with P >1. 5 GeV / c or two oppoite ign electron with P e >. GeV / c. hi trigger i relevant in electing event a B J /ψk S that will be ued for meauring both in β and the excluive B meon lifetime and alo to earch for EWK penguin decay uch a B () l l. B (*) K l l and other rare decay uch a: B Meon Ma ( MeV/c ) PG/ PG/σ (CF ) σ(cf)/ (CF)/σ(PG(PG) B B B u d J / ψk J / ψk * J / ψϕ ± ± ± ± ± ± ABLE I. Comparion of the meaured Run II meon mae with PG value.

7 Num. event / 5 MeV CF Run II preliminary, φπ, φkk -1 Feb, Luminoity 1.5 pb KKπ ma [GeV] a) b) c) * FIG 6. a) ignal recontructed in the * Kππ decay mode; b) and ignal recontructed in the, φπ,φ KK mode; c) ignal recontructed in the KK decay channel. 3. Charm Phyic he SV B trigger turned out to be extremely efficient alo in electing event enriched in charmed meon. With the expected Run IIA integrated luminoity of fb CF II will be able to collect a charm ample up 1 1 time larger than thoe coming from fixed target experiment (ee able II). Large amount of Cabibbo uppreed K K decay and π π are alo oberved. Other pecie are alo oberved a hown in Fig. 6. irect charm production i eparated from charm coming for B meon decay by looking at the impact parameter. CF II i at preent meauring the differential production cro ection for: *,,, and hadron. Charged mode uch a K K π and neutral mode uch a Λ c π π will be both ued in order to earch for direct CP violation. ecay Channel Event Λ * c π ( Kπ KK ππ Kππ KKπ pkπ Kπ ) ABLE II. Expected yield of hadronic charm decay with1 pb of data.

8 a) b) b) c) d) FIG 7. ranvere ma ditribution for: a) W eν e ; b) W µν µ ; d) W τν τ ; c) Number of track expected and oberved inide the τ jet for W τν τ ignal and for QC background. 3.3 Electroweak Phyic At evatron Collider, the W-boon are produced by hard colliion between the contituent quark and anti-quark of the proton and anti-proton. uring the Run I CF meaured the W boon ma with a preciion of about 8 MeV / c leading to a combined CF and reult of M W = ±.4 GeV / c expecting to meaure the W ma with a preciion of that i the world mot precie meaurement [4]. CF II i δm W 3 MeV / c on an integrated luminoity of fb. We tarted to look to all 3 leptonic decay channel of the W: W ν ( l = e, µ, τ ) uing the data collected till now. he W boon ma i extracted from fitting, with appropriate invariant ma, the tranvere ma ditribution defined a: ν ν E l r r M E p l p. Figure: 7.a, 7.b and 7.d how the W tranvere ma l l ( ) ( )

9 Z e e -, µ µ - a) d) b) c) FIG 8. Z l l invariant ma peak a oberved in: a) central-central electron ample, b) central-plug electron ample, c) plug-plug electron ample and d) in the µ µ channel. ditribution a obtained in the cae of W eν e, W µν µ and W τν τ. In figure 7.c we compare the number of track expected in the τ jet for W τν τ ignal and for the QC background (MC) with the W τν from the data. Event are elected by requiring an iolated electron or muon with P > 5GeV / c τ and the preence of a conitent amount of miing tranvere energy E/ > 5 GeV. By analyzing 1 pb we found 5547 W. he W ignal i quite clean indeed we expect the background fraction not to exceed 7%. hi ample have been ued alo to etimate the production cro ection: σ W BR( W eν e ) =.6 ±.3( Stat) ±.6 ( Lu min oity) nb and found to be conitent with the Run I meaurement. We have already clean Z e e and Z µ µ ample. Figure 8.a, 8.b, 8.c how the Z e e invariant ma a recontructed for central-central electron, central-plug electron and uing electron having both the leg into the plug detector. Fig 8.d how the Z µ µ invariant ma a recontructed on a data ample of 6 pb. Analyi on the Z τ τ

10 E (e ) = 73 GeV E (e - ) = 56 GeV ME = 43 GeV E (je t 1 ) = 35 GeV E (je t ) = 34 GeV FIG 9. Run II dielectron op candidate a diplayed uing the C II event diplay. channel i underway and, alo for thi analyi, preliminary reult will viable for the winter conference. 3.4 op Quark Phyic At evatron, top quark are predominantly pair-produced, with each top quark decaying to a W and to a b quark: t t WbWb. he increae in the center of ma energy from 1.8 ev to 1.96eV wa mainly motivated by the conitent rie of the top quark production cro ection of 3 35%. CF II i expecting to collect a top quark ample 3 time bigger than in run I, auming an integrated luminoity of fb. At preent we are finalizing important tool uch a the b-tagging baed both on jet probability and on b hadron vertex diplacement and the jet correction. CF II can expect to meaure, uing the firt fb the top quark ma with a preciion of δm t 3GeV / c and top quark ma meaurement wa:. uring the Run I the combined CF M t = ± 5.1 GeV / c [5]. Combined knowledge of M t and M W will allow u to et a more tringent limit on the Standard Model Higg ma [6]. In figure 9 we how one of the Run II di-electron top candidate ( t t W W bb e ν ee ν ebb ). Both in the central cutaway and lego plot i poible to ee the two candidate electron and jet preent in the final tate.

11 FIG 1. Integrated luminoity required per experiment to either exclude at 95% C.L. or dicover with a 3σ or 5σ ignificance a SM Higg boon. 4. Higg Potential At evatron the Higg boon i expected to be produced mainly via gluon fuion or in aociation with W or Z boon. Although the gluon fuion mode give the mot important contribution to the Higg production, it will be overwhelmed by the large QC background. herefore, given ufficient luminoity, the mot promiing SM Higg dicovery mechanim * for m H < 13GeV / c conit of q q annihilation into a virtual V (V =W, Z ), where the * virtual V Vh SM followed by h SM bb and the leptonic decay of the V that will erve a a trigger. he main background for thi mode will be Wb b and WZ procee. For 1 GeV / c < mh < 19GeV / c, where the Higg i produced with a vector boon, it will * * mainly decay into W W tate with ubequent decay ( W, Z)W * W * l ± ν l ± ν jj. For thi cae election criteria require two lepton with P > 1GeV / c having the ame charge and two eparate jet with E jet > 15GeV / c and the preence of miing tranvere energy. he main background in thi cae i WZjj production. Among variou analye underway ome intereting reult could alo come from the ue of neural network technique. he integrated luminoity required per each evatron experiment, to exclude a 115 GeV / c SM Higg boon at 95% C.L. i fb.

12 5. Concluion In thi paper we reviewed recent CF II reult reporting on the tatu of the detector and it upgrade. he CF II detector i preently performing very well and ha collected until the middle of June 5 pb -1 of data. We expect by the end of thi year to reach an integrated luminoity of pb. he undertanding of the detector performance i very advanced o many phyic analyi are in progre. With the new detector capabilitie a broad phyic program i within our reach. We expect to preent new intereting reult by the winter Acknowledgment I wih to thank the Organizer of the SUSY Conference for the excellent conference and their kind hopitality. 7. Reference [1] F. Abe et al. [CF Collaboration], he CF-II detector: echnical deign report, FERMILAB-PUB E (1996). [] F. Abe et al. [CF Collaboration], Nucl. Intrum. Meth. A71, (1988). [3] S. Bailey, Nucl. Intrum. Meth. A46, (1). [4] A. Kotwal, FERMILAB-FN-716, Aug. 1pp; [5] K. Sliwa, Acta Phy.Polon.B33: ,. [6] M. Carena et al., FERMILAB-CONF--79-, SCIPP--37, Oct. 185pp.