Impact of LHCf on BRAN and beam monitoring Y.Itow, H.Menjo (Nagoya University) The 1 st 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 cm -2 s -1 Luminosity < 0.8 x cm -2 s -1 Bunch intensity 4x10 10 ppb (  *=18m) 1x10 10 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 cm -2 s -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.

Geometry The 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 (9.9cm t ): 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 displacements The Detector #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 Detector #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 factors Detector #1Detector #2 X displacement Y displacement

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=10 29 Shower center position is assumed as – true hit position for gamma’s – 1mm smearing for hadrons Beam test result  ~ 200  m 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) 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 LHCf Detector #1Detector #2 2 cm x 2 cm 4cm x 4cm2.5cmx2.5cm3.5cmx3.5cm s s 0s 0s hadrons Detector acceptance for single inelastic collision ( The detectors at “ the zero degree” position.) For L= cm -2 s -1, ~ 10kHz inelastic collisions  0 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) True posfitted posDifference Hadron flux ( in cm ) Fit with the hadron flux at the 2cmx2cm calorimeter only H.Menjo

Results (detail) difference Gamma flux dist.hadron flux dist. True pos ( in cm) H.Menjo