Impact of LHCf on

BRAN and beam monitoring Y.Itow, H.Menjo (Nagoya University)

The 1st TAN integration workshop

Mar10, 2006

Typical run conditions

• Beam parameters for commissioning is desirable for us !

Beam parameter

Value

# of bunches < 43

Bunch separation

> 2 sec

Crossing angle 0 rad

140 rad downward

Luminosity per bunch

< 2 x 1028 cm-2s-1

Luminosity < 0.8 x 1030 cm-2s-1

Bunch intensity 4x1010 ppb (*=18m)

1x1010 ppb (*= 1m)

( No radiation problem for 10kGy by a “year” operation with this luminosity )

LHCf running scenario

• Phase-I– Parasite running during the early stage of LHC

commissioning in 2007– Remove the detector when luminosity reaches

1030cm-2s-1 level for radiation reason• Phase-II

– Re-install the detector at the next opportunity of low luminosity run

– Presumably parasite running during TOTEM run in 2008

• Phase-III– Future extension for p-A, A-A run with upgraded

detectors.

GeometryThe Detector #1

The Detector #2

Side view

LHCf 3 Cu bars

• The 1st three Cu bars will be replaced by the LHCf detector– 3 Cu bars (9.9cmt): 21 r.l. / 2 int

– LHCf has 22 W plates (0.7cmt): 47(44) r.l. / 1.7 int

• Difference is in their coverage– 2x2cm+4x4cm (detector #1)– 2.5x2.5cm+3.5x3.5cm(detector #2)

• Effect on BRAN measurements– Reduction of shower particles at BRAN– Position dependence on beam displacement– Check by simple simulation ( by H. Menjo )

Solution : If beam displacement is < a few mm, reduction is < 10%. LHCf itself should provide the center of neutral flux instead

BRAN response vs

beam displacement

• Since the LHCf detectors just cover a part of the aperture in front of the BRAN, the response of the BRAN depends on beam displacement.

• The ratio, ( #of neutral hadrons in the LHCf aperture / that for whole aperture) is estimated as a “reduction factor to BRAN” for various beam displacements at the TAN position.

• Here 10K inelastic interactions by the DPMJET3 model were used ( so the result slightly depends on the interaction model)

Flux vs beam displacementsT

he D

etec

tor

#1

The contour maps of energy flux of hadrons (energy×flux)in each aperture , all area (the left) or the LHCf aperture (the right) , are shown for various positions of beam center .

The

Det

ecto

r #2

 

H.Menjo

The BRAN reduction factor vs beam displacements

The Detector #1 The Detector #2

The reduction factors for BRAN response for various positions of beam center.When beam center at the center of beam-pipe, the factors are 0.2 and 0.3 for the Detector #1 and Detector #2, respectively.

H.Menjo

The dependence of the BRAN reduction factor on the beam displacements

The Detector #1 The Detector #2

The relative change of the reduction factors for BRAN with respective to the nominal value for the case of the beam center at the beam-pipe center. If the position of beam center stays within a few mm from the beam-pipe center, the reduction factors do not change more than 10%.

H.Menjo

Summary of BRAN reduction factorsDetector #1 Detector #2

X d

ispl

acem

ent

Y d

ispl

acem

ent

Determination of neutral flux center by LHCf

• LHCf can provide the center of neutral flux from the collisions – LHCf has X-Y position sensitive layers, SciFi and Si for detector

#1 and #2,respectively• However the material of LHCf does not cover uniformly

10cm×10cm aperture– Complex position dependence of shower development– Also bring complex in the position determination by BRAN

• Need to study LHCf capability for position determination

Position sensitive layers

particles

Simulation • MC simulation to provide position and energy of

incident particles at LHCf– 1E6 interactions (DPMJET)– corresponding to 100sec data w/ L=1029

• Shower center position is assumed as– true hit position for gamma’s– 1mm smearing for hadrons

Beam test result

~ 200m No position dependence of

Particle density distribution

H.Menjo

2-D Fit of flux distribution

• Use true entering positions

• For hadrons, 1mm position resolution assumed

• Fit X-Y distribution of the flux with “2-D exponential” fucntion. (not used 2mm from edges)  

})()(exp{).( 20

20 yyxxbayxD

H.Menjo

Fitting accuracy for the neutral flux center( at the 2x2cm calorimeter center )

Fitted with hadron flux at 2x2cm only

H.Menjo

Fitting accuracy for the neutral flux center( with Y offset of - 5mm)

Fitted with hadron flux at 2x2cm only

H.Menjo

Conclusion• If the displacement of the beam center is less than a few

mm, change of BRAN reduction factor is less than 10%.• Neutral center can be measured with

– < 0.5mm if the flux center is well inside the 2cmx2cm calorimter – a few mm if the flux center is out side of calorimeters

• The results should be interaction model dependent. However it can be tuned by the data itself.

• Next step– Full detector simulation including the BRAN

Typical event rate on LHCfDetector #1 Detector #2

2 cm x 2 cm 4cm x 4cm 2.5cmx2.5cm 3.5cmx3.5cm

s 0.067 0.046 0.095 0.072

0s 0.0007 0.0015

hadrons 0.015 0.0052 0.020 0.0078

Detector acceptance for single inelastic collision( The detectors at “ the zero degree” position.)

For L= 1029 cm-2s-1, ~ 10kHz inelastic collisions

0 hadrons

Rate at

2cm x 2cm

670 Hz 7 Hz 150 Hz

30% analysis efficiency Is assumed for hadrons

Results ( the flux center inside the calorimeter)

x y x y x y0.0 0.0 - 0.009 0.012 - 0.009 0.0120.5 0.5 0.487 0.482 - 0.013 - 0.0180.3 - 0.1 0.268 - 0.121 - 0.032 - 0.0210.1 - 0.7 0.109 - 0.661 0.009 0.039

真の値との差ハドロン分布

真の位置 Fitting結果ハドロン分布

 

True pos fitted pos Difference

Hadron flux Hadron flux

( in cm )Fit with the hadron flux at the 2cmx2cm calorimeter only

H.Menjo

Results (detail)

x y x y x y x y x y0.0 0.0 0.049 - 0.048 - 0.076 - 0.535 0.049 - 0.048 - 0.076 - 0.5350.0 - 0.1 0.056 - 0.143 0.018 - 0.099 0.056 - 0.043 0.018 0.0010.5 0.5 0.525 0.409 0.397 0.389 0.025 - 0.091 - 0.103 - 0.1110.3 - 0.1 0.328 - 0.183 0.216 - 0.110 0.028 - 0.083 - 0.084 - 0.0100.1 - 0.7 0.238 - 0.894 0.320 - 1.055 0.138 - 0.194 0.220 - 0.3551.0 - 1.0 1.152 - 1.207 1.019 - 0.959 0.152 - 0.207 0.019 0.0411.7 - 0.2 1.786 - 0.255 1.409 - 0.239 0.086 - 0.055 - 0.291 - 0.0391.0 1.0 1.034 0.963 1.004 1.004 0.034 - 0.037 0.004 0.0040.0 - 1.5 0.139 - 1.459 - 0.004 - 1.577 0.139 0.041 - 0.004 - 0.0770.5 - 2.0 1.338 - 3.477 0.407 - 1.622 0.838 - 1.477 - 0.093 0.3782.0 - 2.0 3.490 - 3.481 3.425 - 2.948 1.490 - 1.481 1.425 - 0.9482.0 2.0 2.031 1.983 2.223 1.999 0.031 - 0.017 0.223 - 0.001

ガンマ線フラックス分布 ハドロン分布真の値との差difference

Gamma flux dist. hadron flux dist.

x y x y x y x y x y0.0 0.0 0.049 - 0.048 - 0.076 - 0.535 0.049 - 0.048 - 0.076 - 0.5350.0 - 0.1 0.056 - 0.143 0.018 - 0.099 0.056 - 0.043 0.018 0.0010.5 0.5 0.525 0.409 0.397 0.389 0.025 - 0.091 - 0.103 - 0.1110.3 - 0.1 0.328 - 0.183 0.216 - 0.110 0.028 - 0.083 - 0.084 - 0.0100.1 - 0.7 0.238 - 0.894 0.320 - 1.055 0.138 - 0.194 0.220 - 0.3551.0 - 1.0 1.152 - 1.207 1.019 - 0.959 0.152 - 0.207 0.019 0.0411.7 - 0.2 1.786 - 0.255 1.409 - 0.239 0.086 - 0.055 - 0.291 - 0.0391.0 1.0 1.034 0.963 1.004 1.004 0.034 - 0.037 0.004 0.0040.0 - 1.5 0.139 - 1.459 - 0.004 - 1.577 0.139 0.041 - 0.004 - 0.0770.5 - 2.0 1.338 - 3.477 0.407 - 1.622 0.838 - 1.477 - 0.093 0.3782.0 - 2.0 3.490 - 3.481 3.425 - 2.948 1.490 - 1.481 1.425 - 0.9482.0 2.0 2.031 1.983 2.223 1.999 0.031 - 0.017 0.223 - 0.001

真の位置True pos

( in cm)

H.Menjo