- Email: [email protected]
Study of jet production in p-N interactions at √s500 GeV in EAS multicore events
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ELSEVIER
PROCEEDINGS SUPPLEMENTS
Nuclear Physics B (Prec. Suppl.) 75A (1999) 225-227
Study of jet production in p-N interactions at v/S multicore events
500 G e V in EAS
Vigorito Carlo for the E A S - T O P Collaboration * The cross section for large PT jet production for transverse momentum 10 _< PT < 30 GeV/c and rapidity interval 1.6 _< *l _< 2.6 in p-N ("Air") interactions is studied from the analysis of multicore Extensive Air Showers at xF ~ 500 GeV the projectiles being the leading particles interacting at atmospheric depth between 250 and 390 gem -~. The obtained jet production cross section in p - N interactions with respect to p - p interactions is c~JETt,-~= ~rr,-v~ET. _t '-~ with (~ = 1.53 -t- 0.07 for A ~ 14. The result agrees with p-nucleus accelerator measurements at x/~ ~- 30 GeK in the same range of transverse momentum and rapidity interval.
1. I n t r o d u c t i o n In Extensive Air Showers (EAS) experiments multicore events have been observed since '60's [1 3] and their interpretation as due to jet production has lead to first d a t a on production cross sections [,i]. In such experiments the jet is produced by the leading particle interacting at altitudes 7 < z < 11 k m above the sea level at typical energies ~ ~ 500 (.,el . [n the present paper we report a m e a s u r e m e n t of the jet p r o d u c t i o n cross section or_ _JET N at VCS~ 500 ( ; c V for 10 < PT <_ 30 G e V / c and pseudorapidity 1.6 < 7/ _< 2.6. This is c o m p a r e d with existing p - 1) and p - n u c l e u s d a t a at colliders [5,6] and fixed target experiments [7]. From the point of view of cosmic rays physics, the effect is of interest for experiments exploiting the high energy c o m p o n e n t in the core region to draw conclusions on the p r i m a r y composition. 2. T h e e x p e r i m e n t The E A S - T O P array is located at C a m p o Imperatore, central Italy, 2005 m a.s.1. (National (]ran Sasso L a b o r a t o r y ) . T h e EAS core investigations are performed by means of its calorimeter. The shower size and arrival direction are obtained from the electromagnetic detector [8]. The E A S - T O P calorimeter is a parallelepiped of (12 × 12 × ?,) m 3 and consists of 9 identical *For the c o m p l e t e list. of a u t h o r s see A . C h i a v a s s a , " S t u d ies of t h e k n e e in the e l e c t r o n a n d m u o n c o m p o n e n t s of E x t e n s i v e Air 54howers a t E A N - T O P " , t h e s e P r o c e e d i n g s .
planes. Each of the active plane is m a d e of two streamer tube layers for m u o n tracking, one layer of quasi proportional tubes (3 x 3 c m 2 section, 12 m length) for hadron calorimetry separated by 13 cm thick iron absorbers, for a total depth of 818 g c m -2. The read-out of the quasi proportional tubes is performed by means of a m a t r i x of 840 pads (40 × 38 em 2) placed on the top of each level and covering a total area of 128 m u. T h e active layers of the upper plane (9 th) are unshielded and operate as a fine grain detector of the electromagnetic c o m p o n e n t of EAS cores. A model of the response of the quasi p r o p o r t i o n a l chambers has been developed and checked experimentally. Such model has been included into a simulation of hadronic cascades ( C O R S I K A - H D P M ) initiated in the atmosphere and p r o p a g a t e d t h r o u g h the calorimeter. 3. T h e d a t a s e l e c t i o n Tile shower size and core location are reconstructed t h r o u g h a fit to the N K G f o r m u l a of recorded particle numbers Ni,j at the 9 th (upper) level. Events with core located inside a fiducial area of 8 × 8 m 2 centered on the calorimeter and with zenith angle 0 < 350 are selected. For shower size Ne > 105 the reconstruction efficiency is e > 95%, the resolution ±g~ We < 15% and the accuracy on arrival direction ere ~ 0.50; in 70% of showers the fitted core position is found at distance d < 70 crn from the pad with m a x i m u m recorded n u m b e r of particles. 5"522 EAS have been analysed in the ~ize remge
0920-5632/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII S0920-5632(99)00250-9
C Vigorito/Nuclear Physics B (Proc. SuppL) 75.4 (1999) 225-227
226
I(
O 9 th L A Y E R PADS
,
• E.M. COUNTERS * SCINTILLATORS
I0 4
i
¢J ~-~10
.__.1o ~I0 2
~10
i* •
I0 ~
:"
10
1 ,--I
I0
l0
10
-2[
L-1
I0
1
10
10 2
10
Core distance (m)
1052'~ < N~ < 105.6o, i.e. energy beetwen 500 and 1000 T e V for primary protons. Multicore events (see figure l) are selected from the analysis of the e.m. component detected on the uppermost layer of the calorimeter by applying a cluster algorithm to the matrix of the quantities: t (N~j' = N~,5 - -N~j).
(1)
For each subcore, the quantities: 2(1
P9 =
8
E'
~%:j
(i,j]
and
$8 =
20
E E 'Ni,j, k
k=l
10 3
10 4
10 5
$8 (particles)
Figure 1. A multicore EAS: the reconstructed lateral distribution function of the main shower and the central region are shown.
5'i,j = ~,: ~(N~,j) ~i,j
10 2
(2)
(i,j)
are defined. The sum involves the 20 most significant pads within 1 m from the subcore position on the nppermost plane (P9, i.e. the electromagnetic content) and, for internal ones, around the projected position following the EAS direction (5'8 integrated over the 8 internal layers, i.e. the hadronic and high energy e.m. contents). -Ni,j for the upper layer is obtained from the NKG fit., for internal ones from the pads at the same distance r fl'om the main core, not belonging to the subcore structure. The resulting scatter plot P 9 - ,~'8 for physical events is shown in figure 2. The same plot is shown in figure 3 for simulated primary proton showers of different, energies initiated at the top and at different atmospheric
Figure 2. Scatter plot of cluster patterns (P9,$8) of the detected secondary structures in 130 multicore EAS. depths ranging from 8 to 10 k m a.s.l.. From the comparison of figure 2 and 3 it results that the pattern of the selected subcore structures falls in the region characterized by intermediate starting levels in the atmosphere. Subcore energies and production heights are obtained through a fit to the quantities P9 and $8 (for details see ref. [9]). Typical values are: 10 < Es < 50 T e V and 5 < h < 9 K m above the detectors while distances from axis are 1.5 < r < 7 m. By means of ad hoc simulations the following quantities have been computed and included in the analysis: a) the correction eE, due to the jet fragmentation, to be applied to the subcore energy E~; b) the efficiency for subcore detection eD (N~, E~, r); c) the geometrical rapidity acceptance cR(r/). The transverse momentum for each subcore has been obtained using the expression: E 3 -r
PT = e ~ ' h" (3) The uncertainty in the PT measurements is: A P T / P T ~ 50%. At the quoted intermediate interaction levels the projectiles contributing to the events can be associated to the leading particles inside the showers. Their energy spectrum has been derived from the primary one by scaling the corresponding energy to the mean production depth of our events with an attenuation
C I'Tgorito/Nuclear Physics B (Proc. Suppl.) 75.4 (1999) 225-227
p -
"~10 4
TOP (100-1100
TeV)
• p - 8 < h < 1 0 k m a.s.I. (15-40 T e V )
o
A~
g+
-'
227
.
[-
+
•
10 ~
..~..d ~ . . . . ~ ' ~ . -.
..:.-
~. :-
l0
_¢_ • EAS-TOP DATA (p-Air)
10
• COLLIDER DATA (p-p)
• 10
10 2
10 3
10 4
10 5
$8 (particles)
10
. . . .
I
10
. . . .
I
15
. . . .
I
20
. . . .
I
. . . .
25 30 PT (GeV/c)
Figure 3. Scatter plot of cluster patterns (P9,$8), showing the different behaviour between top initiated showers and showers initiated at lower level.
Figure 4. PT distribution in multicore EAS ( p A i r interactions) compared with the expected one from the p - f collider cross section data.
length A ~ 100 gcrn -~:. At the mean production height z ~ 9000 m a.s.l., i.e. atmospheric depth X ~ 270 gcm-":, the leading particle energy, averaged over the primary spectrum in the range 5 0 0 - 1000 Te+V here analysed, is Ei.p ~ 125 T e V corresponding to v G ~ 500 G e V for p - p interactions. The accepted region of pseudo-rapidity 7.8 < ~/ _< 8.8, where ~R(TI) exceeds 40%, corresponds to 1.6 _< 71. . . . < 2.6 in the c.m. of the interaction.
a = 1.53 + 0.07 is obtained. This measurement agrees with the accelerator d a t a obtained in fixed target experiments at v ~ ~ 30 G e V . It is shown that no change of the value of c~ occurs between x/~ ~ 30 G e V and x/~ ~ 500 GeV.
4. T h e R e s u l t s Tile resulting PT distribution for 1.6 < r/c.m. _< 2.6 is shown in figure 4 where the shift due to the uncertainties in the measurements of PT have been included. In the same figure the ( d N / d P T ) p - v distribution expected from the cross section d
REFERENCES
1. Hazen W . E et al.,Phys. Rev.,90,(1953) 496; Matano T. et al.,Can.J.Phys.,46,(1968),S56; Bakich A.M et al.,Can.J.Phys.,46,(1968),S30; Bosia G.et al.,Nuovo Cimento C,3,(1980),215 2. Aglietta M. et al., Proc. XXIV ICRC, Roma, 1, (1995) 430; Aglietta M. et al.,Nnovo Cimento C,18,(1995),663 3. Lindvasky A.S., Proc. XXV ICRC, Durban, HE, (1997) 169 4. Chudakov A.E. et al., Proc. XVII ICRC, Paris, 6, (1981) 183 5. Appel J.A. et al.,Phys.Lett.B,160,(1985) 349 6. Di Lella L., Ann. Rev. Nucl. Part. Sci., 35, (1985), 107 7. Cronin J . W et al., Phys. Rev. D, 11, (1975) 3105; Gomez R. et al., Phys. Rev. D, 35, (1987), 2736 8. Aglietta M. et al., Nucl. Instr. and Meth. A, 336, (1993) 310; Aglietta M. et al., Nucl. Instr. and Meth. A, in press (1998) 9. Vigorito C., Ph. D. Thesis, 1998
ELSEVIER
PROCEEDINGS SUPPLEMENTS
Nuclear Physics B (Prec. Suppl.) 75A (1999) 225-227
Study of jet production in p-N interactions at v/S multicore events
500 G e V in EAS
Vigorito Carlo for the E A S - T O P Collaboration * The cross section for large PT jet production for transverse momentum 10 _< PT < 30 GeV/c and rapidity interval 1.6 _< *l _< 2.6 in p-N ("Air") interactions is studied from the analysis of multicore Extensive Air Showers at xF ~ 500 GeV the projectiles being the leading particles interacting at atmospheric depth between 250 and 390 gem -~. The obtained jet production cross section in p - N interactions with respect to p - p interactions is c~JETt,-~= ~rr,-v~ET. _t '-~ with (~ = 1.53 -t- 0.07 for A ~ 14. The result agrees with p-nucleus accelerator measurements at x/~ ~- 30 GeK in the same range of transverse momentum and rapidity interval.
1. I n t r o d u c t i o n In Extensive Air Showers (EAS) experiments multicore events have been observed since '60's [1 3] and their interpretation as due to jet production has lead to first d a t a on production cross sections [,i]. In such experiments the jet is produced by the leading particle interacting at altitudes 7 < z < 11 k m above the sea level at typical energies ~ ~ 500 (.,el . [n the present paper we report a m e a s u r e m e n t of the jet p r o d u c t i o n cross section or_ _JET N at VCS~ 500 ( ; c V for 10 < PT <_ 30 G e V / c and pseudorapidity 1.6 < 7/ _< 2.6. This is c o m p a r e d with existing p - 1) and p - n u c l e u s d a t a at colliders [5,6] and fixed target experiments [7]. From the point of view of cosmic rays physics, the effect is of interest for experiments exploiting the high energy c o m p o n e n t in the core region to draw conclusions on the p r i m a r y composition. 2. T h e e x p e r i m e n t The E A S - T O P array is located at C a m p o Imperatore, central Italy, 2005 m a.s.1. (National (]ran Sasso L a b o r a t o r y ) . T h e EAS core investigations are performed by means of its calorimeter. The shower size and arrival direction are obtained from the electromagnetic detector [8]. The E A S - T O P calorimeter is a parallelepiped of (12 × 12 × ?,) m 3 and consists of 9 identical *For the c o m p l e t e list. of a u t h o r s see A . C h i a v a s s a , " S t u d ies of t h e k n e e in the e l e c t r o n a n d m u o n c o m p o n e n t s of E x t e n s i v e Air 54howers a t E A N - T O P " , t h e s e P r o c e e d i n g s .
planes. Each of the active plane is m a d e of two streamer tube layers for m u o n tracking, one layer of quasi proportional tubes (3 x 3 c m 2 section, 12 m length) for hadron calorimetry separated by 13 cm thick iron absorbers, for a total depth of 818 g c m -2. The read-out of the quasi proportional tubes is performed by means of a m a t r i x of 840 pads (40 × 38 em 2) placed on the top of each level and covering a total area of 128 m u. T h e active layers of the upper plane (9 th) are unshielded and operate as a fine grain detector of the electromagnetic c o m p o n e n t of EAS cores. A model of the response of the quasi p r o p o r t i o n a l chambers has been developed and checked experimentally. Such model has been included into a simulation of hadronic cascades ( C O R S I K A - H D P M ) initiated in the atmosphere and p r o p a g a t e d t h r o u g h the calorimeter. 3. T h e d a t a s e l e c t i o n Tile shower size and core location are reconstructed t h r o u g h a fit to the N K G f o r m u l a of recorded particle numbers Ni,j at the 9 th (upper) level. Events with core located inside a fiducial area of 8 × 8 m 2 centered on the calorimeter and with zenith angle 0 < 350 are selected. For shower size Ne > 105 the reconstruction efficiency is e > 95%, the resolution ±g~ We < 15% and the accuracy on arrival direction ere ~ 0.50; in 70% of showers the fitted core position is found at distance d < 70 crn from the pad with m a x i m u m recorded n u m b e r of particles. 5"522 EAS have been analysed in the ~ize remge
0920-5632/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII S0920-5632(99)00250-9
C Vigorito/Nuclear Physics B (Proc. SuppL) 75.4 (1999) 225-227
226
I(
O 9 th L A Y E R PADS
,
• E.M. COUNTERS * SCINTILLATORS
I0 4
i
¢J ~-~10
.__.1o ~I0 2
~10
i* •
I0 ~
:"
10
1 ,--I
I0
l0
10
-2[
L-1
I0
1
10
10 2
10
Core distance (m)
1052'~ < N~ < 105.6o, i.e. energy beetwen 500 and 1000 T e V for primary protons. Multicore events (see figure l) are selected from the analysis of the e.m. component detected on the uppermost layer of the calorimeter by applying a cluster algorithm to the matrix of the quantities: t (N~j' = N~,5 - -N~j).
(1)
For each subcore, the quantities: 2(1
P9 =
8
E'
~%:j
(i,j]
and
$8 =
20
E E 'Ni,j, k
k=l
10 3
10 4
10 5
$8 (particles)
Figure 1. A multicore EAS: the reconstructed lateral distribution function of the main shower and the central region are shown.
5'i,j = ~,: ~(N~,j) ~i,j
10 2
(2)
(i,j)
are defined. The sum involves the 20 most significant pads within 1 m from the subcore position on the nppermost plane (P9, i.e. the electromagnetic content) and, for internal ones, around the projected position following the EAS direction (5'8 integrated over the 8 internal layers, i.e. the hadronic and high energy e.m. contents). -Ni,j for the upper layer is obtained from the NKG fit., for internal ones from the pads at the same distance r fl'om the main core, not belonging to the subcore structure. The resulting scatter plot P 9 - ,~'8 for physical events is shown in figure 2. The same plot is shown in figure 3 for simulated primary proton showers of different, energies initiated at the top and at different atmospheric
Figure 2. Scatter plot of cluster patterns (P9,$8) of the detected secondary structures in 130 multicore EAS. depths ranging from 8 to 10 k m a.s.l.. From the comparison of figure 2 and 3 it results that the pattern of the selected subcore structures falls in the region characterized by intermediate starting levels in the atmosphere. Subcore energies and production heights are obtained through a fit to the quantities P9 and $8 (for details see ref. [9]). Typical values are: 10 < Es < 50 T e V and 5 < h < 9 K m above the detectors while distances from axis are 1.5 < r < 7 m. By means of ad hoc simulations the following quantities have been computed and included in the analysis: a) the correction eE, due to the jet fragmentation, to be applied to the subcore energy E~; b) the efficiency for subcore detection eD (N~, E~, r); c) the geometrical rapidity acceptance cR(r/). The transverse momentum for each subcore has been obtained using the expression: E 3 -r
PT = e ~ ' h" (3) The uncertainty in the PT measurements is: A P T / P T ~ 50%. At the quoted intermediate interaction levels the projectiles contributing to the events can be associated to the leading particles inside the showers. Their energy spectrum has been derived from the primary one by scaling the corresponding energy to the mean production depth of our events with an attenuation
C I'Tgorito/Nuclear Physics B (Proc. Suppl.) 75.4 (1999) 225-227
p -
"~10 4
TOP (100-1100
TeV)
• p - 8 < h < 1 0 k m a.s.I. (15-40 T e V )
o
A~
g+
-'
227
.
[-
+
•
10 ~
..~..d ~ . . . . ~ ' ~ . -.
..:.-
~. :-
l0
_¢_ • EAS-TOP DATA (p-Air)
10
• COLLIDER DATA (p-p)
• 10
10 2
10 3
10 4
10 5
$8 (particles)
10
. . . .
I
10
. . . .
I
15
. . . .
I
20
. . . .
I
. . . .
25 30 PT (GeV/c)
Figure 3. Scatter plot of cluster patterns (P9,$8), showing the different behaviour between top initiated showers and showers initiated at lower level.
Figure 4. PT distribution in multicore EAS ( p A i r interactions) compared with the expected one from the p - f collider cross section data.
length A ~ 100 gcrn -~:. At the mean production height z ~ 9000 m a.s.l., i.e. atmospheric depth X ~ 270 gcm-":, the leading particle energy, averaged over the primary spectrum in the range 5 0 0 - 1000 Te+V here analysed, is Ei.p ~ 125 T e V corresponding to v G ~ 500 G e V for p - p interactions. The accepted region of pseudo-rapidity 7.8 < ~/ _< 8.8, where ~R(TI) exceeds 40%, corresponds to 1.6 _< 71. . . . < 2.6 in the c.m. of the interaction.
a = 1.53 + 0.07 is obtained. This measurement agrees with the accelerator d a t a obtained in fixed target experiments at v ~ ~ 30 G e V . It is shown that no change of the value of c~ occurs between x/~ ~ 30 G e V and x/~ ~ 500 GeV.
4. T h e R e s u l t s Tile resulting PT distribution for 1.6 < r/c.m. _< 2.6 is shown in figure 4 where the shift due to the uncertainties in the measurements of PT have been included. In the same figure the ( d N / d P T ) p - v distribution expected from the cross section d
REFERENCES
1. Hazen W . E et al.,Phys. Rev.,90,(1953) 496; Matano T. et al.,Can.J.Phys.,46,(1968),S56; Bakich A.M et al.,Can.J.Phys.,46,(1968),S30; Bosia G.et al.,Nuovo Cimento C,3,(1980),215 2. Aglietta M. et al., Proc. XXIV ICRC, Roma, 1, (1995) 430; Aglietta M. et al.,Nnovo Cimento C,18,(1995),663 3. Lindvasky A.S., Proc. XXV ICRC, Durban, HE, (1997) 169 4. Chudakov A.E. et al., Proc. XVII ICRC, Paris, 6, (1981) 183 5. Appel J.A. et al.,Phys.Lett.B,160,(1985) 349 6. Di Lella L., Ann. Rev. Nucl. Part. Sci., 35, (1985), 107 7. Cronin J . W et al., Phys. Rev. D, 11, (1975) 3105; Gomez R. et al., Phys. Rev. D, 35, (1987), 2736 8. Aglietta M. et al., Nucl. Instr. and Meth. A, 336, (1993) 310; Aglietta M. et al., Nucl. Instr. and Meth. A, in press (1998) 9. Vigorito C., Ph. D. Thesis, 1998