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ψ-particle inclusive distributions
Volume 76B, number 2
THE
PHYSICS LETTERS
A-DEPENDENCE
OF
J/0-PARTICLE
INCLUSIVE
22 May 1978
DISTRIBUTIONS
Yu.M. ANTIPOV, V.A. BESSUBOV, N.P. BUDANOV, Yu.P. GORIN, S.P. DENISOV, S.V. KLIMENKO, A.A. LEBEDEV, Yu.V. MIKHAILOV, A.I. PETRUKHIN, S.A. POLOVNIKOV, V.N. ROINISHVILI l D.A. STOYANOVA and F.A. YOTCH
Institute for High Energy Physics, Serpukhov, USSR Received 23 March 1978
• • • 2 . . • The differential cross sections do / d ~¢and f~o/dPt of inclusive J/O production by 43 GeV/c zr- off Be, Cu and W nuclei have been measured. Fitting do/dPt ~ A (Pt) we observed the increase of c~with Pt" •
.
2
Oe
'~
We have reported earlier [1] on the A-dependence of the J/ff production cross section in n - A interactions at 43 GeV/c. Here we present the x =Pl/Pmax and p2 distributions o f J/ff production off Be, Cu and W obtained in the same experiment. The experimental setup, the "Sigma" spectrometer and the data processing procedures have been described elsewhere [1,2]. The reaction 7r-A -+ J/ff + ... was identified by the decay J/ff -+/a+/J - . For the J/ff inclusive distributions we selected the events with muon pair massMu~ , in the band [Mu~ - Mj/¢ I~ rj/ , where Mj/¢ and Fj/o are the apparent mass and width o f the J / i peak in the dimuon mass spectrum. The background in the mass band selected contributed 5 - 2 0 % for different targets [ 1] and was assumed to have the same x and p2 distributions as the J/if-particle. The normalized cross sections (1/o)(da/dx) o f the J/ff production are presented in fig. la. Their shapes are similar; the broad maximum at x ~ 0.4, observed for the copper target [3,4], is present also on berillium and tungsten targets. The result of fitting da/dx with the power l a w A a is shown in fig. lb. The exponent a does not depend on x within statistical errors and is consistent with the value o f a = 0.92 + 0.06 obtained earlier [1] for the J / i total inclusive cross sections. The independence o f a on x was also found in nA J/ff + ... at 300 GeV/c [5]. The J/ff differential production cross sections I I n s t i t u t e o f P h y s i c s , Tbilisi, U S S R .
•
•
2
+t+
,6
0.8
"' +
8e
+
"++++ 0
. . . . .
i
0.6
Cu
+
0.8
+ w
0
+
. . . . . . 0
0.0|
0.3
I,
0.6
,
,
0.9 X
.
Fig. 1.(a) Normalized inclusive cross sections (1/a)(da/dx) of J/qJ-particle production on Be, Cu and W; (b) x dependence of the exponent a.
do/dp 2 are presented in fig. 2a. The straight lines are the fits in the form exp(-bPt2). The slopes are: bBe = 2.1 + 0.3, bcu =- 1.45 -+ 0.25, b w = 1.3 + 0.3 (GeV/c) - 2 . The value of bBe is consistent with that obtained by us earlier [2], bcu is the same as in refs. [3,4]. It is worth mentioning that the slope b is de235
Volume 76B, number 2
PHYSICS LETTERS
22 May 1978
20
1,2 v
1
15 ~0.8
i
_+_
l
i
o,1
\ ,~
I
i
0,2
i
0,5
i
i
~,o 2~
2 (GeV/e)2
Pt
Fig. 3. The same as in fig. 2b, but with different background subtraction procedure (see text).
Cu
%-
lo
0.2
0.6
1.0
1.4
__tz P
(GeM/c) z
section in each bin was determined by fitting dimuon mass spectra as described in ref. [1]. The a ( p 2 ) dependence for these cross sections is shown in fig. 3, it is similar to that in fig. 2b. The exponent a determined for the adjacent mass band 2 5 0 0 - 2 8 0 0 MeV is equal to 0.7 + 0.2 and does not depend on p2 within the errors, i.e. the observed increase of a with p2 is due to J/q/production. Similar behavior o f a ( p 2) was found for the inclusive production o f rr+-, K +-, K 0, p and ~ [ 6 - 1 0 ] . It should be mentioned that in nA ~ J / q / + ... at 300 GeV/c [5] no changes o f a with p2 were observed.
Fig. 2.(a) The J/~0 inclusive cross sections do/dp~ for Be, Cu and W; (b) p~ dependence of the exponent a.
References
creasing with increasing A. The result o f the fit do/dD 2 2 . --t ~ A (Pt) lS shown in fig. 2b. One can see that a is increasing from the value a = 0.74 + 0.09 a t p 2 = 0.1 up to a = 1.14 + 0.14 atPt2 = 1.1 (GeV/c) 2. Since the p2-distribution o f J / q / m a y differ from that o f the background in the same mass band we have tried to remove this background by the following method. All the/a+/2 - events were divided into 3 p t2 bins for each target used and the J / q / p r o d u c t i o n cross
[1] Yu.M. Anfipov et al., Phys. Lett. 72B (1977) 278. [2] Yu.M. Antipov et al., preprint IHEP 76-42 (Serpukhov, 1976). [3] M.J. Gorden et al., Phys. Lett. 68B (1977) 96. [4] Yu.B. Bushnin et al., preprint IHEP 77-93 (Serpukhov, 1977). [5] M. Binkley et al., Phys. Rev. Lett. 37 (1976) 571. [6] U. Becker et al., Phys. Rev. Lett. 37 (1976) 1731. [7] D.A. Garbut et al., Phys. Lett. 67B (1977) 355. [8] J.W. Cronin et al., Phys. Rev. D l l (1975) 3105. [9] L. Kluberg et al., Phys. Rev. Lett. 38 (1977) 670. [10] O. Conception et al., preprint CRN/HE 77-10 (Strasbourg, 1977).
236
THE
PHYSICS LETTERS
A-DEPENDENCE
OF
J/0-PARTICLE
INCLUSIVE
22 May 1978
DISTRIBUTIONS
Yu.M. ANTIPOV, V.A. BESSUBOV, N.P. BUDANOV, Yu.P. GORIN, S.P. DENISOV, S.V. KLIMENKO, A.A. LEBEDEV, Yu.V. MIKHAILOV, A.I. PETRUKHIN, S.A. POLOVNIKOV, V.N. ROINISHVILI l D.A. STOYANOVA and F.A. YOTCH
Institute for High Energy Physics, Serpukhov, USSR Received 23 March 1978
• • • 2 . . • The differential cross sections do / d ~¢and f~o/dPt of inclusive J/O production by 43 GeV/c zr- off Be, Cu and W nuclei have been measured. Fitting do/dPt ~ A (Pt) we observed the increase of c~with Pt" •
.
2
Oe
'~
We have reported earlier [1] on the A-dependence of the J/ff production cross section in n - A interactions at 43 GeV/c. Here we present the x =Pl/Pmax and p2 distributions o f J/ff production off Be, Cu and W obtained in the same experiment. The experimental setup, the "Sigma" spectrometer and the data processing procedures have been described elsewhere [1,2]. The reaction 7r-A -+ J/ff + ... was identified by the decay J/ff -+/a+/J - . For the J/ff inclusive distributions we selected the events with muon pair massMu~ , in the band [Mu~ - Mj/¢ I~ rj/ , where Mj/¢ and Fj/o are the apparent mass and width o f the J / i peak in the dimuon mass spectrum. The background in the mass band selected contributed 5 - 2 0 % for different targets [ 1] and was assumed to have the same x and p2 distributions as the J/if-particle. The normalized cross sections (1/o)(da/dx) o f the J/ff production are presented in fig. la. Their shapes are similar; the broad maximum at x ~ 0.4, observed for the copper target [3,4], is present also on berillium and tungsten targets. The result of fitting da/dx with the power l a w A a is shown in fig. lb. The exponent a does not depend on x within statistical errors and is consistent with the value o f a = 0.92 + 0.06 obtained earlier [1] for the J / i total inclusive cross sections. The independence o f a on x was also found in nA J/ff + ... at 300 GeV/c [5]. The J/ff differential production cross sections I I n s t i t u t e o f P h y s i c s , Tbilisi, U S S R .
•
•
2
+t+
,6
0.8
"' +
8e
+
"++++ 0
. . . . .
i
0.6
Cu
+
0.8
+ w
0
+
. . . . . . 0
0.0|
0.3
I,
0.6
,
,
0.9 X
.
Fig. 1.(a) Normalized inclusive cross sections (1/a)(da/dx) of J/qJ-particle production on Be, Cu and W; (b) x dependence of the exponent a.
do/dp 2 are presented in fig. 2a. The straight lines are the fits in the form exp(-bPt2). The slopes are: bBe = 2.1 + 0.3, bcu =- 1.45 -+ 0.25, b w = 1.3 + 0.3 (GeV/c) - 2 . The value of bBe is consistent with that obtained by us earlier [2], bcu is the same as in refs. [3,4]. It is worth mentioning that the slope b is de235
Volume 76B, number 2
PHYSICS LETTERS
22 May 1978
20
1,2 v
1
15 ~0.8
i
_+_
l
i
o,1
\ ,~
I
i
0,2
i
0,5
i
i
~,o 2~
2 (GeV/e)2
Pt
Fig. 3. The same as in fig. 2b, but with different background subtraction procedure (see text).
Cu
%-
lo
0.2
0.6
1.0
1.4
__tz P
(GeM/c) z
section in each bin was determined by fitting dimuon mass spectra as described in ref. [1]. The a ( p 2 ) dependence for these cross sections is shown in fig. 3, it is similar to that in fig. 2b. The exponent a determined for the adjacent mass band 2 5 0 0 - 2 8 0 0 MeV is equal to 0.7 + 0.2 and does not depend on p2 within the errors, i.e. the observed increase of a with p2 is due to J/q/production. Similar behavior o f a ( p 2) was found for the inclusive production o f rr+-, K +-, K 0, p and ~ [ 6 - 1 0 ] . It should be mentioned that in nA ~ J / q / + ... at 300 GeV/c [5] no changes o f a with p2 were observed.
Fig. 2.(a) The J/~0 inclusive cross sections do/dp~ for Be, Cu and W; (b) p~ dependence of the exponent a.
References
creasing with increasing A. The result o f the fit do/dD 2 2 . --t ~ A (Pt) lS shown in fig. 2b. One can see that a is increasing from the value a = 0.74 + 0.09 a t p 2 = 0.1 up to a = 1.14 + 0.14 atPt2 = 1.1 (GeV/c) 2. Since the p2-distribution o f J / q / m a y differ from that o f the background in the same mass band we have tried to remove this background by the following method. All the/a+/2 - events were divided into 3 p t2 bins for each target used and the J / q / p r o d u c t i o n cross
[1] Yu.M. Anfipov et al., Phys. Lett. 72B (1977) 278. [2] Yu.M. Antipov et al., preprint IHEP 76-42 (Serpukhov, 1976). [3] M.J. Gorden et al., Phys. Lett. 68B (1977) 96. [4] Yu.B. Bushnin et al., preprint IHEP 77-93 (Serpukhov, 1977). [5] M. Binkley et al., Phys. Rev. Lett. 37 (1976) 571. [6] U. Becker et al., Phys. Rev. Lett. 37 (1976) 1731. [7] D.A. Garbut et al., Phys. Lett. 67B (1977) 355. [8] J.W. Cronin et al., Phys. Rev. D l l (1975) 3105. [9] L. Kluberg et al., Phys. Rev. Lett. 38 (1977) 670. [10] O. Conception et al., preprint CRN/HE 77-10 (Strasbourg, 1977).
236