Pub-94-268-E

8/3/2019 Pub-94-268-E

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Fermi National Accelerator Laboratory

FERMILAB-Pub-94/268-E

Search for Charged Bosons Heavier than the W inp F Collisions at ds=1800 GeV

F. Abe et. alThe CDF Collaboration

Fermi National Accelerator LaboratoryP. 0. Box 500, Batavia, Illinois 60510

August 1994

Submitted to Physical Review Letters

0 Operated by Universities Research Association Inc. under Contract No. DE-AC02-76CH03000 with the United States Department of Energy

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Disclaimer

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Governme/rt uor any agency thereof, nor any oftheir employees, makes any warranty, express or implied, or assumes any legal liabilityor responsibility for the accuracy, completeness, or usefulness of any information,apparatus, product, or process disclosed, or represents that its use would not infringe

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CDF/PUB/EXOTIC/PUBLIC/2640FERMILAB-PUB-94/268-E

Search for Charged Bosom Heavier than

the Win p p Collisions at 6=1800 GeV

F. Abe,‘” M . G. Alhrow,” D. Amidei,“‘J. An~o.s,~~ C. Anna),-Wiese, G. Apollinari,Z6

H. Areti,’ M. Atac,; P. Auchincloss,‘” I;. Azfar,2’ P. Azzi,?” N. Bacchetta,‘* W. Badget t,‘6

M. W. Bailey,18 J. B~o,“~ I’. dc Bar-baro,Zs A. Burharo-Galtieri,‘~ V. E. Barnes,‘4B. A. Barnett,” P. Bnrtnlini,” G. Rnucr,15 T. Baumnnn,” F. Bcdeschi,‘” S. Rehrends,”

S Belforte 13 G. Bcllcrrini,23 J. Bcllin~er,33 D. Bcnj;m~ in,3’ J. Benlloc.h,” J. Bensinger,”

D. benron,“‘A. Berel\.as,7 J. P. Berge,; S. Bertolucci,” A. Hhalti,26 K. Bicn,,” ht. Binkfey,’

F. Bird,‘” D. Biselfo,ZO R. E. Blair,’ C. Blockcr,Z3 A. Bodek,“; W. Bokhari, is V. Bolognesi,*3

D. Borroletto,24 C. BowelI,” 1’. Boulos,” G. Brandenburg,” E. Buckle) -Gee’-,’ 1-l. S. Budd,2s

K. Burkett,16 G. Buserto,70 A. B)x>n-Wngncr,7 K. L. f3),rum,’ J. Cammcrata,‘~ C. Campagnari,7

M. Campbell, I6 A. Cancr,i W. Carithcrs, I4 D. Carlsmith,,’ A. Caslro,2(’ Y. Cen,” F. Cervelli,*3

J. Chapman,16 hf.-‘1’. Chcnfi,‘s (;. Chiarclfi, s T. Chik;‘m;‘tsu,3’ S. Cihangir,’ A. G. Clark,Z3

M. Cot~al,‘~ PIl. Contreras,” 1. Conwa!~,2i J. Cooper,i hf. Cordelli,8 D. Crane,’

J. D. Cunningham,” -I‘. Daniels’” f:. DeJon#h,; S. Dcfchamps,i S. Dclf’Agncflo,~3 M. Dell’Orso,*3

L. Demortier,Z6 B. Denb\p,Z3 hl. Dcninno,’ P. F. Denvent,‘” T. l>e\~lin,Zi M. Dickson,‘s

S. Donati,‘” R. B. Druckcr,” A. L)LIII~,‘~ K. Einsn~eiler,‘-’ J. E. Efi;ts,i R. Efy,‘l

E. Engels, Jr.,” S. Eno,; II. Errede,‘O S. 13-rcde,‘~~ Q Fan.‘” B. Farhat ‘s I, Fiori,’B. Flaugher,; G. W. Foster,7 hf. f~ranklin.” hl. f3-aut.sc.hi,‘8 J. I’rccman,i’ J. J:ricdman,‘s

H. Frisch,j A. Fry,‘O .I’. A. Fucss,’ Y. f.ukui, I3 S. f:unaki,3’ G. Ca~fiardi,23 S. Caleotti,23

M. Gallinaro,2c’ A. F. Garfmkef,~4 S. Gwr,7 D. W. Gcrdes,‘” I’. Giannerti,L3 N. Giokaris,Z6

P. Giromini,8 L. Gladney,” L>. Glenzinski,‘2 Irf. Gold,‘8 J. Gonzalez,” A. Gordon,g

A. T. Gosf~aw,~ K. Goufianos,‘” II. Grxsmann,G A. Grer~~af,21 G. (;riec*o,?3 L. Groer,” C. Grosso-

Pifcher,5 C. f-faber, ” S. R. lluhn,7 ft. Ifamil~on,“ IX. Iiandfcr,33 1~. bl. Hans,“-’ K. Hara,j’

B. Harraf,” R. hf. ffarris,7 S. A. fiaugcr,(’ J. flauser,4 C. flrc\~,k,27 J. fltinrich,” D. Cronin-

Hennessy,6 R. tfoflebcck ,~’ 1.. flollo~.a~~,~~‘A. 116fschcr,” S. lfong,‘6 G. flo~k,~* P. Hu,Z*

B. T. Huffman,” Ii. Hughes,‘” I’. Hurst,‘) J. tfuslon,17 J. Huth,9 J. H_\4en,7 M. fncagli,‘3

J. Incandela,’ H. Iso,~* H. Jensen,’ C. P. Jessop,” II. Joshi,; R. W. Kadef,*-l E . Kajfasz,‘a

T. Kamon Jo T

R. D. Kennedy:”

. Kaneko -‘I D. A. Kardelis,lu II. Kasha,“’ Y. Kate,‘” L. Keebfe,JO

R. Kephar;,’ P. Kesten,” D. Kestenbaum,9 R. f% Keup,‘o H. Keutelian,’

F. Keyvan, D. H. Kim,; H. S. Kim,” S. B. Kim,16 S. H. Kim j* Y. K. Kim,” L. Kirsch,3P. Koehn,‘” K. Kondo,3’ J. Konigshcrg,9 S. Kopp,; K. Kordai,l’ W. Koska, : E. Ko\ucs,‘~

W. K~wald,~ hf. Krasherfi,‘” j. Krclll,i I\I. Krusc,‘-’ S. 1:. Kuhfmann, E. Kuns,”

A. T. Laasanen,Z4 N. l;aha~~c~a,~~’ . Lan~mcl,4 J. I. L.amoureus; ‘I’. LcCompre,‘o S. Leone,‘3

J. D. Lewis,; P. Limon,7 hf. l.indqcn,-’ I‘. 1\1. I.iss,“’ N. Loc%~w,2’ C. Loomis,Z7 0. Long,”

M. Loreti,zo E . H. Low,” J. I.LI,~(’ I). lucchcsi,‘” C. H. l.whini,‘” P. I.ukens,i I’. Maas,

K. Maeshim&; A. blaghaf4an,2” I’. ~laksimo\%*,’ i hl. ~lunguno,2~’ J. ~fansnur,li hf. Mariotti,‘3

J. P. Marriner,; A. I\lnrlin,‘” J. A. J. bfatthew,‘s 1~. hIattingl!,,15 P. blclnt\,re,3(’ P. Melese,26

A. Menzione,‘j E. hfeschi,‘-’ G. blichail,3 S. hfikamo,‘.’ hl. hliller,5 K. ~filfer,li T. Mimashi,31

S. Miscetti,8 hi. I\fishina, I3 H. blitsushio,“’ S. \fi).ashin,J1 Y. ~forila,‘3 S. hloulding,‘b

J. Mueller,27 A. Mukherjce,; ‘I: ~lulfer,4 1’. ~lusgra\*e,” 1.. I’. Nakac ,“’ I. Nakano,3’ C. Nelson,’

D. Neuberger, C. Newn~an-tlolmcs,i I. Nodulman,’ S. O&~wa,~ ’ S. It. Oh,6 K. E. Oht,34

R. Oishi,“’ T. Okusaw, I9 C. Pa~fiaronc,2~’ R. Paofclli,Z~~ V. Papadimilriou,i S. Park,’

J. Patrick,; C. Paulettu,23 bl. Paulini,” 1.. l’escar~,~~’ bl. 1). l’eters,‘4 I’. J. Phiflips,6G. Piacentino,’ bl. Pillai,” R. l’funkctl,i L. f’ondrom,33 N. f’roduir,‘-’ J. f’roudfoot,’ F. Ptohoq9

G. Punzi,‘” K. Ragan,’ ’ F. liimondi,’ I.. fIisu)ri,2.q hl. I~o~lc.h-l(cllino,~’ W. J. fIohertson,6

T. Rodrigo,; J. f:o’nano,s 1.. Roscnson,‘i W. K. Sahunloto,“5 D. Saftzbcrg,5 A. Sansoni,s

V. Scarpine, 3o A. Schindlcr,‘-’ I’. Schlahac.h,” Ii. li. SchmiJ’,7 1\f. I’. Sc.hnlidl,34 0. Schneider,14

G. F. Sciacca,‘” A. Scrihano,23 S. Sc&x,7 S. Seidcl’s Y. Sei\.a;” G. Sganos,’ ’ A. Sgolacchia,*

M. Shapiro,*’ N. Irl. Shaw,” Q. Shcn,‘-’ I’. I:. Shcpard,” bl. Shimojimi~,3’ h1. Shochet,s

J. Siegrist,” A. Sill ii’ P. Sincnq” I’. Sinffh,” J. Skarha,‘Z K.

Submitted to Physidal Review Letters August 24, 1994.

Sliwa,zZ D. A. Smith,‘3

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F. D. Snider,12 L. Song,’ T. Song,‘” J. Spalding,’ L. Spiegel,’ P. Sphicas,15 A. Spies,”L. Stanco,z” J. Steele,“” A. Stefanini,‘” K. Strahl,” J. Strait,; D. Stuart,’ G. Sullivan,j

K. Sumorok,lj R. L. Swartz, Jr.,l” T. Takahashi, 19 K. Takikawa,“’ F. Tartarelli,‘” W. Taylor,”

Y. Teramoto,‘” S. Tether,‘” D. Theriot,‘J. Thonlas,29 T. L. ThomaqLS R. Thun,16 M. Timko,32

P. Tipton,‘s A. Titov,zB S. Tkaczyk,; K. Tollefson,‘” A. Tollestrup,’ J. Tonnison,*”

J. F. de Troconiz,” J. Tseng,” M. Turcotte,zQ N. Turini,’ N. Uemura,31 F. Ukegawa,”

G. LJnal,*l S. van den Brink,” S. Vejcik , lll,lG R. Vidal,’ hI. Vondracek,‘” R. G. Wagner,’R. L. Wagner,’ N. Wainer, 7 R. C. Walker,?” G. Wan&z3 J. Wang,” M. J. Wang,‘s Q. F. Wang,‘6

A. Warburton,” G. Watts,‘” T. Watts,- 7i R. Webb,“” C. Wendt,“j H. Wenzel,14

W. C. Wester III,‘-’ T. Westhusing,lc’ A. B. Wicklund ,’ E. Wicklund,’ R. Wilkinson,”

H. H. Williams,” P. Wilson,” B. L. Winer,“s J. Wolinski,30 D. Y. Wu,16 X. Wu,z3 J. Wyss,‘O

A. Yagil,’ W. Ya0,l-l K. Yasuoka,31 Y. Ye, I1 G. P. Yeh,’ P. Yeh,z8 M. Yin,6 J. Yoh,’ T. Yoshida,lg

D. Yovanovitch,7 1. Yu,“” J. C. Yun,’ A. Zanetti,13 F. Zetti,‘” L. Zhang,j3 S. Zhang,16

W. Zhang,” and S. Zucchelli’

(CDF Collaboration)

1Argomle National Laboratory, Argonne, Illinois 60439

21stituto Nazionale di Fisica Nucleare, University of Bologna, I-40126 Bologna, Italy

3Brandeis University, Waltham, Massachusetts 022544University of California at Los Angeles, Los Angeles, California 90024

‘llniversity of Chicago, Chicago, Illinois 60637

‘Duke University, Durham, North Carolina 2708

‘Fermi National Accelerator Laboratory, Batavia, Illinois 605 10

sLaboratori Nazionali d i Frascati, lstituto Nazionnle di Fisica Nucleare, I-00044 Frasca ti, Italy

‘Harvard University, Cambridge, Massachusetts 02 138

“University of Illinois, Llrbana. Illinois 61801

“Institute of Particle Physics, McGill University, Montreal H3A 2T8, and University of Toronto, Toronto MSS 1A7, Canada

I2The Johns Hopkins Ilniversity, Baltimore, Maryland 2 I2 18

13National Laboratory for High Energy Physics (KEK), Tsukuba, Ibaraki 303, Japan

14Lawrence Berkeley Laboratory, Berkeley, California 94720

15Massachusetts histitute of Technology, Cambridge, Massachusetts 02 139

‘%Jniversity of Michigan, Ann Arbor, Michigan 18 109

1’Michigan State University, East Lansing, Michigan 48824

“University of New Mexico, Albuquerque, New Mexico 87 13 1

190saka City Ilniversity, Osaka 568. Japan

2OUniversita di Padova, Instituto Nazionale di Fisica Nucleare, Sezione di Padova, I-3 5 13 1 Padova, Italy

2lUniversity of Pennsylvania, Philadelphia, Pennsylvania 19104

22University of Pittsburgh, Pittsburgh, Pennsylvania 15260

231stituto Nazionale di Fisica Nucleare. University and Scuola Normale Superiore of Pisa. I-56100 Piss, Italy2”Purdue Ilniversity, \Yest Lafayette. Indiana 4i907

2%Jniversity of Rochester, Rochester, New York 14627

2’Rockefeller University, New York, New York 10021

2’Rutgers University, Piscataway. New Jersey 08854

“Academia Sinica, Taiwan 11329, Republic of China

*%uperconducting Super Collider Laboratory, Dallas, Texas 75237

3%%xas A&M University, College Station, Texas 778-13

3 ‘University of Tsukuba, Tsukuba, Ibaraki 303, Japan

32Tufts University, Medford. Massachusetts 02 I55

33University of \Visconsin, Madison, Wisconsin 53706

34Yale llniversity’. New Haven, Connecticut 06511

“Visitor

13 August 1334

2

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PACS numbers: 13.85.Rt-11, 2.15.cc, 14.80.Er

This paper presents a search for new, hea\y, charged bosons, W’, through the

Abstract

We have searched for new, heals),, charged bosons, W’, through the decay

W’+ev in p$ collisions at 6 = 1.8 TeV. The data used in the search represent

19.7 pb-1 collected by CDF at the Fermilab Te\:atron Collider. Limits are placed oncr-B(pjF+W’-+ev) as a function of Iz_lwl. Assuming standard couplings of the W’ to

fermions, we establish the limit kfwl > 652 GeV/c2 (95% C.L.).

process pp+ W’dev. III its simplest form, the W’ appears as a heavier version of the

left-handed W, which has a mass J,iw = 80 GeV/cl. In this case, the primary decay

of the W’ for very large masses is W’+WZ. However, in extended gauge models,[l]

proposed to restore left-right symmetry lo rhe weak force, the right-handed W’ can

decay with large probability to right-handed k)r~ pairs, since it is espectedL21 that

the coupling at the W’ WZ” vertex is multiplied by a left-right mixing angle

5 -(fig? thereby suppressing the decay W’+ WZO. This search assumes that the

decay W’+WZo is suppressed and that the VR is sufficiently light that the process

W’+k’~i$ can occur.

The coupling of the W’ to fermions, which determines the production cross

section of the W’ in pF collisions, is not known. Lorentz-invariance and

renormalizability restrict the W’-fermion coupling to be of the form

$2 vda+ bY.dYpW~~jllij, where a and b are constanls and (Jij is the CKM matrix

element connecting fermions i and j. SU(Z)L gauge-invariance in the Standard

Model leads to the V-A character of the weak inreraction wirh ;I = 1, b = -1. In the

Standard Model, furthermore, the CKM matrix is approsimately diagonal: UL - 1. No

3

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such constraints esist for a and h or for the right-handed CKhI matrix in the context

of extended gauge models. With this couplin, u the partial wridth to fermions is

i-y W’+fifj) =

(a2 ; q(“i~~~~w~) , “ii ,2,

[II

where Nc is the color factor of 3 for quarks and is 1 for leptons. The case of “standard

strength couplings,” where k2 = $aZ+ b-‘) = 1, holds true in the Standard Model. It

also holds in models in which the left- and right-handed gauge sectors couple to

matter with equal strengths, ~IIOWII as left-right symmetry. Manifest left-right

symmetry further impliesIJR = ~JL.

The cross section limits in this paper assumeUR = UL, and the mass limit further assumes a 2 = 1.

Many previous’ searches have been conducted for the W’. For very light

neutrino masses, the most stringent limits are astrophysical or cosmological (all 90%

C.L. unless otherwise noted): for m, < 1 MeV constraints from big bang

nucleosynthesis[31 imply kIw# > 1 TeV, and the energetics of Supernova 1987A can in

some models implyfhl Mw > 16 TeV. Assuming manifest left-right symmetry, a limit

of Mw, > 1.3 TeV has also been derived[sl using experimental data from muon

decay,[61 the measured difference between the KL and KS masses,[-/l the semileptonic

branching ratio b+Mv,[81 Bd-Td mixing,[91 and neutrinoless atomic double beta

decay.[lol Finally, direct searches for the decay W’ +k’v at pF colliders have

established the limitflll Mw, > 520 GeV/cP (95% C.L.) for the case of manifest left-

right symmetry.

We search for the W’ in 177 collisions through the decay W’+ev . This search

is specific to neither right- nor left-handed bosons, but in the case of the WR’ it is

assumed that the VR is noninteracting and stable. It is not assumed that the VR is

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massless, only that it is much lighter than the W’ (for A~w, = 600 GeV/cP and

mV = 60 GeV/cl, for esample, our cross section lim it belo\\’ is affected by < l%, and

the effect on the mass liinir is negligible). We search for the signature of a new

Jacobian peak in the trans\:erse mass (defined beloiv) spectrum of electron + missing

transverse momentum data and set a limit on @B(p p+ W’+ev).

This search was conducted using a dataset with an integrated luminosity of

19.7 + 0.7 pb-1 collected with the Collider Detector at Fermilab (CDF) during the 1992-

1993 Tevatron collider run. Detailed descriptions of the detector can be found

elsewhere. 1121 The portions of the detector releltant to this search are (i)

electromagnetic and hadronic calorimeters co\:ering the pseudorapidity range

1~1 < 4.2 and arranged in a projective tower geometry; (ii) a drift chamber (CTC)

immersed in a 1.4 T solenoidal magnetic field for tracking charged particles in the

range 1771< 1.4; (iii) a time-projection chamber (VTX) for vertex finding; and (iv)

two arrays of scintillator hodoscopes located on either side of the detector for

triggering and luminosity monitoring.

To select candidate events, we require an electron in the central, barrel region

of the detector (1~1 < 1.05) with ET > 30 Ge\/Ildl and PT > 13 GeV/c, as measured in

the CTC. In addition we require the electron track to be isolated in the CTC, requiring

Iso(trk) < 5 GeV/c, where fso(trk) is defined as the scalar sum of the PT of all tracks

except the electron track within a cone centered on the electron of half-angle

AR = 0.25 in 77-q space, where AR = 4 (A@)? + (Aq)” . The ratio of energy in the

hadron (Had) and electromagnetic (EM) calorimeter towers of the electron cluster is

required to satisfy Had/EM < 0.055 + 0.045 x A transverse momentum

imbalance is required to signal the presence of the noninteracting neutrino. We

require @- > 30 GeV, where the missing trans\:erse momentum (ET) is defined as

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the negative of the vector sum of the ET in all calorimeter towers with InI < 3.6.

Finally, the pp interaction point, w.hich is distributed by, an approsimate gaussian

with width 0Z = 26 cti about the center of the detector, is required to satisfy

IZjnh < 60 cm and the total accidental calorimeter energy’ not in time with the pj7

collision (measured by the timing in the hadron calorimeters) is required to be

Edout-of-time) < 100 GeV. There are 10815 events passing these cuts. Of these, 82

events with second isolated, tracks with PT > 10 GeV/c pointing to electromagnetic

clusters are removed from the sample as Zo candidates. Also, 229 e\.ents with clusters

of tracks in the CTC in lvhich A$ < 18”, w:here A@ is the angle between the tracks and

the ET vector, and in which the tracks point to calorimeter cracks, are removed from

the search sample as mismeasured QU3 jet events (“dijets”), leaving 10534 events.

From a study of electrons from ZO+e+e- decays, the efficiency of the isolation,

Had/EM, out of time energy, and vertex cuts is found to be (95f2) % for

Mwl = 80 GeV/cZ. The Had/EM efficiency, furthermore, agrees well with the

efficiency found from an electron testbeam and is observed to be flat up to E = 175

GeV. A Monte Carlo simulation of the detector shows no degradation in the Had/EM

efficiency up to E = 500 GeV. A Monte Carlo calculationllSl including radiative

effects indicates that the isolation efficiency will drop by w 1% between Mwf = 80 and

600 GeV/cZ due to conversions of photons radiated by W’ electrons in the tracking

volume. We estimate the efficiency of the Z[) removal cuts for W’ events to be

(99.9+0.1)%, and the dijet removal cuts are estimated to be (99.5+0.2)% efficient for W’

events.

The primary background to the W’ signal is W+ev decay. Several other

processes can also mimic the W’ signal. The process W-+rv+evvv has a signature

similar to that of the W’, but at much louver trans\.erse mass. The process ZO+e+e-,

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where one electron is detected and the other is lost because it falls into an

uninstrumented region of the detector, can produce the signal of an electron and ET,

as can QCD dijet events, lvhere one jet passes our electron selection criteria and the

other is mismeasured or falls into an uninstrumented region of the calorimeter. Weestimate the number of Z(j+e+e- and W-+zv decays contaminating the search sample

using the ISAJfl Monte Carlo program[l61 and a detector simulation. We normalize to

the measured[l71 cross sections @B(~~-+Z~~-+e+e-) and mB(p~-+W+ev). We find that

the number of Zo events remaining in the sample is 57 + 17 events and the

background from W+zvis 150 L- 45 e\.ents. The QCL?dijet background is estimated[l8]

by studying a data sample of e\:ents \vith an “electron” + k?y., %,here the “electron” has

Iso(trk) > 6 GeV/c. These events are presumably mismeasured dijets. We study the

efficiency of our dijet remo\Jal cuts on this sample and normalize to the number (229)

of events in the sample removed using these cuts. We estimate that the number of

dijets left in the sample is 211 + 40 events. After background subtraction, there are

Ncand = 10086 eligible W plus W’ candidates. Figure 1 shows the transverse mass

distribution of the 10534 events and the expected contribution of the backgrounds,

where MT I ~I!?~ET(~-cos(A$)) and A @ is the azimuthal angle between the

eleCtrOn and ET. We observe 5 events with b/~ > 200 GeV/d, while 2.2 events are

expected from QCO dijet events and 1.8 events are espected from W+ ev decays.

The acceptance, Aw’, is defined as the efficiency for W’ events to pass the

kinematic cuts on the electron and neutrino and for the electron to be in the fiducial

region of the calorimeter. The acceptance is determined using a Monte Carlo

program which generates W’ events using the leading order diagram qT+W’, and

decays the W’ into an electron and a neutrino. We use the MRSD-’ structure

functions.[l91 The effects of higher order diagrams for W’ production are mimicked

by giving the bosons PT according to a pre\>ious measurement[20] of the Pr

7

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spectrum. The dependence of the PI‘ spectrum \\,ith lzwl is sma11.[21] The lepton

momenta are passed through a simulation of the detector response. Systematic

uncertainties in the acceptance calculation come from the choice of parton

distribution functions (1.7%), the modeling of the detector response (1.3%), the effect

of higher-order diagrams (0.8%)) [- -1 and the uncertainty in the Py distribution

(0.6%). The total relative uncertainty’ in AWN is found to be 3%. The W’ decay width

used in the acceptance calculation is calculated from Equation 1, and includes the

decay W’-+th when kinematically al1oFved.t * 3 1 The W’ acceptance for

Mwf = 80 GeV/$ is found to be AW N = 22% and to increase with Mwj to a plateau of

57% for iz/lwl > 400 GeV/G. The difference in acceptances for left- and right-handed

W’ is negligible.

To determine a limit on rB(p?+W’+ev), a binned log-likelihood fit to the

transverse mass spectrum in Figure 1 is performed. The transverse mass spectrum is

fit to the sum of three components: W’-+ev decays, W+ev decays, and other

backgrounds. The fraction of the data that is from W’ decays is determined from the

fit. The observed number of events, .ui, in each bin of the transverse mass spectrum

is compared to the expectation, pi, per bin, where /fi = (Nc,,d -a) Wj + aH + Bckj

and Ncand = 10086 is the number of candidates after background subtraction. Here,

the background normalization is known bin-by-bin, and the normalization of the

known W shape and the W’ shape for a given W’ mass is determined from the fit. The

parameter a is required to lie in the range (0.0 5 CI I IV~~~~~).[*~] The case a = 0

corresponds to no W’events.

The probability function P(a) is computed for each W’ mass, where P(a) is the

probability of obtaining the value a as determined from the likelihood. The

systematic uncertainties in the normalization from the acceptance, backgrounds,

8

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efficiencies, and luminosity and the systematic uncertainty, in the h1-1‘shape from the

W PT are used to “smear” the probabilit!. distribution ~(a).[*;] The 95% C.L. upper

limit on the W’ content in the data is obtained from the point a where

ji&a’)da’ = 0 .35, whereP(a) is the smeared probability, distribution. For very high

W’ masses, where there are no e\‘ents in the data, the fit returns a maximum allowed

W’contribution of 3 e\‘ents, as expected from Poisson statistics.

The 95% upper limit on the W’ cross section times branching ratio is obtained

using the 95% C.L. for a :

sB (95% C.L.) = a (95%)

Aw~&M/$& dtPI

where a (95%) is determined from the fit, .[& dt is the integrated luminosity, AW’ is

the W’ acceptance and EW’ is the efficiency. The 35% C.L. limit on the cross section

times branching ratio as a function of the W’ mass is shown in Figure 2. Also shown

is the expected CPB assuming standard couplings and IJR = lip, as calculated by the

same Monte Carlo as used in the acceptances. For the case of standard couplings to

fermions, we establish the limit fi:lWf > 652 GeV/cZ (95% C.L.), the mass at which our

cross section upper limit intersects with the theoretical prediction.

In conclusion, we have conducted a search for new charged bosons W’

through the decay W’+ev in 19.7 ph-1 of pF collisions at & = 1800 GeV. Assuming

that the W’ has standard couplings to fermions, and assuming the right-handed

neutrino is noninteracting, is stable, and has a mass below MW’, the 95% C.L. limit

Mwl > 652 GeV/c* is obtained.

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We thank the Fermilab staff and the technical staffs of the participating

institutions for their vital contributions. This Ivork \vas supported by the U.S.

Department of Energy and National Science Foundation; the Italian Istituto Nazionale

di Fisica Nucleare; the Ministry ‘of Education, Science and Culture of Japan; the

Natural Sciences and Engineering Rcsearc~h Council of Canada; the National Science

Council of the Republic of China; the A. P. Sloan Foundation; and the Alexander van

Humboldt-Stiftung.

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References

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PI

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r131

u41

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At CDF, cylindrical coordinates r, $, and z, are used, tvhere $J is the azimuthal

angle and z points in the proton beam direction and is zero at the center of the

detector. The pseudorapidity, q, is defined as q = -ln(tan( 8 /2)), where 8 is the

angle with respect to the proton beam direction.

The transverse energy is defined as ET = E x sine, where E is measured in the

calorimeter

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WI R. G. Wagner (unpublished), based on calculations by. F. Berends et al., Z. Phys.

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[I71 F. Abe et. al, Phys. Re\,. D 44, 29 (1391). The results of these measurements are

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U81 S. Kopp, Ph.D. Thesis, The IJniversity of Chicago, 139-I (unpublished).

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1221 We have compared our blonte Carlo with a nest-to-leading order Monte Carlo

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[251 This procedure is given in detail in F. Abe et al., Phys. Rev. D 43, 064 (1991).

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Figure Captions

Figure 1: Transverse mass spectrum of the e\‘ents in the W’ search sample, along

with the expected contributions from backgrounds and from W-+ev

ejlents. The W-+ev cunre is calculated \\ith the I\lonte Carlo program used

to calculate the W’ acceptances.

Figure 2: The 95% C.L. limit on c~f2(~-+W’-+ev) \‘s. the W’ mass. Also shown is the

expected PI?, assuming standard couplings. The point NW = 652 GeV/c2

is our limit, assuming standard couplings.

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Figure 1II 11 11 I I1 I ,’ 1, ‘,’ ,,, 1 I I I I I I I 11

1

16'

tCDF Data (19.7 pb-‘)

W + ev Monte Carlo

All Other Background

$/d.o.f. = 0.89

40 80 120 160 200 240 28

Transverse Mass (GeV/c2)

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Pub-94-268-E

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