Transcript ttt - UV

ILC Machine-Detector Interface
Challenges
Philip Bambade
LAL-Orsay
Workshop on the Future Linear Collider
Gandia, Spain, December 1, 2005
Evolution of


ee
colliders
ILC
SLC
 
VEPP2 
ACO
SPEAR
CEA BYPASS
DCI
VEPP2M

DAFNE
AdA
adapted from K. Yokoya and J.-E. Augustin
Why shift to linear collider ?
storage
ring
• tunnel, magnets,…
• synchrotron radiation losses (RF)
 
 E4 / 
• optimum : equate both costs
 total cost & size  E2
LEP- II Super-LEP
Ecm GeV
180
500
HyperLEP
2000
L
27
200
3200
1.5
12
240
2
15
240
km
E GeV
$tot 109 SF
unacceptable
scaling !
Linear collider concept
idea : cost and size  E
pre-accelerator
few GeV
source
KeV
damping
ring
few GeV
few GeV
bunch
compressor
250-500 GeV
main linac
extraction
& dump
final focus
IP
collimation
from N. Walker
RF
technology
(
gradient, efficient power transfer)
focus
beam phase-space control and stability
 synchrotron radiation still drives design…
LC machine : basic concepts
example :
TESLA
DETECTORS
FINAL FOCUS
POSITRON
SOURCE
LINAC
DAMPING
RING
POLARISED
ELECTRONS
nbNe2 f
L~
HD
4xy
D = disruption
(pinch)
 linac rep. rate f ≪ ring
frequency
 focus beam to small IP size 
 very strong (achromatic) lenses
 ultimate limit (K. Oide) : energy
from synchrotron radiation in lenses
 copious synchrotron radiation
from colliding bunch space-charge
Beam-beam mutual focusing
simulate
collision
with initial
y offset
main tool
at SLC
(and LEP)
SLAC-PUB-6790
detectable
post-IP
deflection
Main ILC specifications from ILCSC
(September 2003)
 Ec.m.s = 0.2 - 0.5 TeV, upgradeable to ~ 1 TeV, capable of
efficiently changing the energy ( scanning)
 L > 500 fb-1 in 4 years after initial year of commissioning
 Stability and precision of beam energy < 0.001
 Electron polarization > 80 %
 2 interaction regions for 2 detectors, with similar Ec.m.s
and L capabilities, among which one should have a
crossing-angle to allow a future upgrade to  collisions
 Optional upgrades: , ee, e, GigaZ, polarized e
Successful SLC (warm / 3 GHz) experience
10
10
9
9
8
8
X * y
7
6
6
5
5
2
7
 x* y (microns )
Beam Size (microns)
IP Beam Size vs Time
4
SLC Design
(x * y)
4
X
3
3
Y
2
2
1
1
0
0
1985
1990 1991 1992 1993 1994 1996 1998
Year
dipole
IP
Dx
sextupoles
0
m

0 1/ m
R
0
0

0
0
at optical focus :
  “depth of focus”
• want small y
• need z  y
 SET z  y
0
0 

0
0 
m
0 

0 1/ m 
FD
L*
 z   y*
hour-glass effect
ILC beam parameter optimization(s)
L/Lnom~ 2.8
nbNe2 f
L~
HD
4xy
nominally
2
N
e Ecm
BS ~
z(xy)2
SET z ~ y
2  n 
L~ Pelectrical BS  z HD  L~ Pelectrical BS HD
ECM
 n, y  y
ECM
 n, y
Design
machine
and
detector
ILC beam parameter
for this set:
L~ Pelectrical BS HD
ECM
 n, y
optimization
 L/Lnom ~ 2.8
Nominal
Luminosity
[cm-2 s-1]
~ 2  1034
BS
 backgrounds
PRECISION
PHYSICS
•ECM resolution
•Forward hermeticity
•Beam-beam systematics
physics  detector  machine
damping ring
compression
injection
LC is open system  “the experiment starts at the gun”
LC performance  “beam-beam interaction dominated”
detector
 LC design & operation : new challenges !
 HEP community strongly involved
 Special needs for some physics topics :
Luminosity + energy + polarization – correlations – forward region – background
crossing-angle choice
Examples of direct impact on
precision physics program
(more work on quantitative assessments needed)
Include detector & physics
performance in global ILC
parameter optimization
1.
Cécile Rimbault
Strongly biases luminosity measurements if not well corrected
precision goal = 10-3-10-4
Cécile Rimbault
2.
Cécile Rimbault
Cécile Rimbault
Comparison with LDC occupancy tolerance
Tolerance : 3 hits/cm2/bx (TDR)
Using :
Nb hits/particle = 3
rough estimate
Surface L1 = 1.5cm* 10cm*2 = 94 cm2
LDC
tesla
nominal
lowQ
largeY
lowP
highLum
NincVD/bx
94
86
39
90
220
240
Nhits/cm2/ bx
3.0
2.7
1.2
2.9
7.0
7.7
high Lum & lowP are beyond the occupancy tolerance
(C. Rimbault)
(Geant4-based)
Precision of secondary vertex charge determination
as function of beam pipe radius
•pipe ddd
•Dddd
•d
Luminosity factor
(S. Hillert & C. Damerell)
study also NEEDED to probe
occupancy tolerance
3.
error 
mtop, msleptons 2  10-4
mW
5 
10-5
reconstruction
top quark threshold
S.Boogert
Beamstrahlung spread dependence with IP beam offset
Nominal
Low Power
M. Alabau
Expect variations larger by factors 2-4 with “Low Power”
for similar IP offset feedback criteria
4.
very forward region  crossing-angle choice
head-on or 2mrad
IP geometry
forward region
calorimetry
at low angle
1. luminosity
2. veto
20 or 14 mrad
Present ILC base-line
Crossing-angle
pros and cons
spent beam extraction (& diagnostics)
(highest energy & luminosity  BS
local solenoid compensation
crab-crossing
Special IR magnet designs
Masking, collimation & backgrounds
Beam diagnostics from pairs
Very forward hermeticity
20 (14) mrad
2 (0) mrad
easier
harder
)
needed
not needed
essential
not essential
yes
slightly harder
? ….under study…. ?
slightly worse
a bit better
slightly worse
a bit better
V. Drugakov
Electron veto efficiencies in BeamCal  need
to be introduced into stau analysis
V. Drugakov
Ring 1
Ring 3
Ring 1
Ring 3
QUESTION TO EXPERIMENTAL
COMMUNITY:
Trade-off between:
1. Luminosity (factor 2-3, up/down)
2. Stronger beam-beam effects:
luminosity spectrum,
forward hermeticity,
backgrounds,
systematics,…
Indirect consequences through
impact on configuration choices
and physics options
2 IR  complementarity, balanced risks and
flexibility with 1 large & 1 small crossing-angle
1 IR (+ 2nd later)  crossing-angle choice affects
articulation of physics program
Only 1 IR  priority to ILC operability at highest
energies & luminosities probably implies large
crossing-angle choice
Options if ILC must start with single IR:
N.B. These arguments are subject to debate in the ILC-WG4
1.
2.
-Best choice to eventually achieve
highest energy and luminosity
beyond nominal goals
-2nd IR optional (later?), dedicated
to precision studies in specific
channels, if physics requires it
- Best conditions for physics at
nominal energies and luminosity
- 2nd IR optional (later?), to enable
the  option and highest energy
and luminosity beyond nominal
goals, if physics requires and after
accumulating learning experience
Increasing awareness to MDI
challenges in HEP ILC
community
Participation of Spanish groups in
this work (along side detector and
physics activities)  important and
very welcome: