lecture

Luminosity measurement at future Linear Collider
Ivanka Božović-Jelisavčić
Vinča Institute of Nuclear Sciences Belgrade
http://www.vinca.rs/hep
PMF Novi Sad 10.12.2012
Outline
- Future linear collider (ILC, CLIC): motivation, physics case
- Forward region at future Linear Collider: design,
challenges
- Luminosity measurement: What do we need to know?
- Vinca at ILC and CLIC
- Reflects & prospects
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
2
Motivation for LC
Synchrotron radiation ∆E ~
1 1
⋅
m4 R
I
nmakes lepton circular machine impossible at higher energies
i
(LEP, 26.67 km, s ≤ 0.2 TeV )
It
n
i heavy/composite particle
iIa
in
l initial state is unknown
i
ts parton energies are lower than
it proton energy
la high (QCD) background
t
te
LHC is discovery machine
a
ti
e
s
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
3
Complementary machine
for precision measurements is needed
ILC, CLIC
- Electrons are point-like
- Initial state known including helicity
- 2Ebeam available for reaction
- Event kinematics reconstructable from the
first principles
- Low background
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
4
Evolution of the LC project
National, multi-national project
- 90’s: TESLA – (DESY) Germany, NLC
(SLAC) USA, JLC – (KEK) Japan
- 2004: TESLA, NLC, JLC →
ILC (International Linear Collider)
- 2005: International Technology
Recommendation Panel (ITRP) decided
for the ‘cold’ technology – based on
TESLA TDR
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
CLIC
- Idea since LEP era
- CERN based
machine
-2004: First report
-2008:
Formalized CLIC-ILC
collaboration
5
LC organization
L. Evans
M. Harrison
10-Dec-2012
S. Stapnes
Ivanka Božović-Jelisavčić
PMF Novi Sad
6
ILC is a ‘cold machine’
Basic ILC RF-structure: 9-cell niobium cavity, 35 MV/m
500 GeV upgradable to 1TeV
+ beam polarization
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
7
CLIC – warm technology
Two-beam acceleration with normal conducting copper
cavities, 100MV/m (CTF3 test facility at CERN)
Energy staging: 500 GeV→3 TeV
+ beam polarization
The choice of actual energy will depend
on LHC 8 TeV and 14 TeV results
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
8
ILC and CLIC parameters
Status of the project
ILC
- length, gradient: 30 km, 35 MV/m
- World-wide project
- cms energy: 500 GeV-1 TeV
- polarization
(e+,
e-):
(~ 400 institutions)
(60%, 80%)
- luminosity: 2⋅10-34 cm-2s-1, 500 fb-1/year
- RDR 2007
- DBD 2012
- bunch space 300 ns (triggerless)
- beam size (σx, σy): (655, 5.7) nm, σz=300 µm
-TDR 2013 (June)
(Depending on several factors) ILC can start in (early) 2020s
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
9
CLIC
- International collaboration
(~ 46 institutions)
- CDR 2012
Project Preparation Phase (2017-2022) sets similar timescale as for ILC
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
10
Physics case for the Linear
Collider
LC will address the same physics program as at
LHC with enhanced precision
- Higgs physics, EW symmetry breaking
CLIC
- SUSY
- Extra space dimensions
- Extended gauge theories
+ Precision EW physics
GigaZ at ILC
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
11
Higgs at LC vs. Higgs at LHC
- Dominant (for light Higgs) bb channel covered by
QCD background
- Coupling to γ/g via loop diagrams
- Higgs is visible at LHC in the full mass range –
light Higgs being a challenge
10-Dec-2012
I. Božović-Jelisavčić
Ivanka Božović-Jelisavčić
- 11 -
PMF Novi Sad
Novi Sad
PMF Novi SadPMF
10.12.2012
… at LC
l
Bjorken process
l
- Higgs can be seen independently
of its decays
- Higgs BRs (HZZ coupling) can be
measured in a model independent way
- ILC is the machine for precision
measurement of (light) Higgs mass
(δmH(SM)~0.04%)
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
13
Precision EW measurements
- Charged current processes can be controlled by proper polarization (i.e.
switch-off single W production)
- All (trilinear) couplings can be measured with an error of a few 10-4
Luminosity has to be controlled at the permille level
WW pair production
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
14
GigaZ
- ILC can be used as a Z factory (109 Z0 in a
few months)
- W mass can be scaned around W-pair
production threshold
- Mw can be measured within 6 MeV with the
total uncertainty of luminosity of 0.25%
-At GigaZ 10-4 relative error of luminosity
Γ
required ( ΓZ , σ had , R1 = had )
Γ1
Without direct observations precision EW could be the only
insight into the new physics
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
15
SUSY
- ILC will test smaller mass scale/lighter
superpartners than LHC
- LSP can be reconstructed from the known
kinematics
- Couplings can be measured due to the
known initial state
- Combination with LHC is needed to
measure (the most of) free parameters with
the enhanced precision
- Dark matter density can be measured with
the precision comparable to the CMB
experiments – consistency check
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
16
Alternative theories
MD [TeV] at CLIC
E6
95% CL
e − e + → γ GKK
δ
2
3
4
5
6
MD [TeV]
LHC
ILC
4.0-7.5
0.5-7.9
4.5-5.9
0.5-5.6
5.0-5.3
0.5-4.2
none
0.5-3.4
none
0.5-2.9
- Various models with extra-dimensions can be probed
(i.e. fundamental scale can be scanned up to 10(15)
TeV in the Model with large extra dimension (CLIC));
- In extended gauge theories larger mass scale (than at
LHC) can be probed for new gauge bosons (i.e. Z’
couplings O(10%)).
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
17
Summary on motivation for LC
- Precision measurements provide strong motivation for the
future linear collider
- LC will address the same physics program as LHC only with
the enhanced precision
- Luminosity is a key quantity for some of the precision
measurement
- Luminosity has to be known with a percent (CLIC) up to a
permille level (ILC), or even better (~10-4) at GigaZ
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
18
Forward region at LC – who do the job design,
challenges
Luminosity measurement –
how difficult a counting experiment could be?
Vinča at LC
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
19
Forward region at LC – who do the job?
Forward CALorimetry Collaboration (FCAL)
http://fcal.desy.de/
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
20
Detector for ILC
FCAL
10-Dec-2012
-VTX 5-layer pixel
- TPC (200points/track)
-SiW ECAL
-Fe-scintillator HCAL
-Si detectors linking VTX-TPC,
TPC-ECAL
- All in 4T field
Ivanka Božović-Jelisavčić
PMF Novi Sad
21
Forward region
Angular coverage:
(80 down to 5) mrad ILC
(110 down to 10) mrad CILC
Detectors:
- LCAL luminometer
- BCAL beam diagnostics,
electron identification,
instantaneous luminosity
- Pair Monitor beam tuning
Technologies:
- LCAL sampling SiW
- BCAL W absorber
+poli(mono)cristaline
diamond/GaAs/rad-hard Si
- Pair Monitor 2⋅105 Si pixel
(0.4, 0.4)mm
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
22
Luminometer at LC
4.5
(Si)
2500
31
78
- small Moliere radius (1.5 cm)
good E resolution
- segmentation (azimuthal/radial): 48/64
- energy resolution: 0.21 [GeV1/2]
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
23
∆E 0.21GeV
=
E
E
1
2
Esh [GeV]
Esh [GeV]
-Stable sampling term vs. shower energy
- Linearity of the integrated deposited
energy vs. shower energy
- Stable E resolution within [38, 69] mrad
(for [31,78] mrad aperture)
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
24

 Ei
Wi = 0, C + ln
 Etot

- resolution in polar angle:
(2.18±0.02)⋅10-2 mrad
- ∆θ =(3.2±0.1)·10-3 mrad
- Polar angle bias can be measured in a
test-beam
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
lθ = 0.8mrad ,



∆L
= 1.6 ⋅10 − 4
L
25
Challenges for the forward region
Purpose:
- Precision luminosity measurement
- Hermeticity (missing energy, multi-jet
final states)
- Efficient electron identification (SUSY
background)
- Shielding to the inner detectors
Challenges:
- LCAL precision measurement, mechanical precision
- BCAL e identification over the huge beamstrahlung
background, extreme radiation hardness (104/BX low
energetic e+e- pairs ~10 TeV/BX or several MGy/year)
+ Read out: high input rate (3.25 MHz), high occupancy
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
26
Luminosity measurement
2.1 nb integrated x-sec.
annual
 ∆L 


L

 stat
- Bhabha scattering is pure ( 99%)
QED process→well theor. described
-Counting experiment
- However, corrections (and their
uncertainties) are present
αi
Lint =
th
σB
exp −
Lint =
∑
dσ
dθ
icor
QED
≈ 32πα 2
< 10 − 4
1
sθ 3
i
ε ⋅σ B
 ∆L  ∆α i

 =
 L i α i
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
27
Vinča at LC – beam induced effects
-
BS+ISR change four-momentum of
the initial state →counting loss in
LCAL
Large effect ⇒ luminosity error ~13%
(ILC), 70% (CLIC)
We proposed a Lorentz invariant method to correct for BS+ISR counting loss
-
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
28
Vinča at LC – beam induced effects
-
-
Event weighting leads to the residual
counting (luminosity) uncertainty ~ 1‰
at ILC
At CLIC: 1.8 ‰ (4.7 ‰) in top 5% (80%90%) of the nominal ECM energy
We proposed a selection for luminosity measurement at ILC
-
We introduce acoplanarity
to reduce fraction of lost events +
physics background
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
29
Vinča at LC – physics background
We estimated for the first time 4-fermion contamination at ILC energies
-
High x-sec ∼ 10s nb,
spectators close to the beam
pipe.
-
However, about 1% of
spectators in the LumiCal.
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
30
Vinča at LC – other (detector
related) systematic effects
We estimated systematics due to energy scale and biases
∆L
= 10 −4
L
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
31
∆L
= 10 − 4 ⇒ 20% control of the
L
sampling term α_res, 10-3 is not an
issue
Bias in θ corresponds to 1.6·10-4
uncertainty of luminosity if taken
as a full size effect
Bhabha energy has to be
controlled better than 100 MeV for
10-4 error of L or 600 MeV for 10-3
∆θ =3.2∙10-6 rad
This is not all…
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
32
Mechanical issues
IN SITU
-
-
LPS prototype monitors
LumiCal as a whole object
Obtained accuracy 0.5µm
in the X-Y plane and 1.5µm
in z direction – two orders
of magnitude better than
required
4 µm for ∆L/L~10-4, ~40 µm for ∆L/L~10-3
Method for measuring
displacement of individual
sensor layers/inner radius
under study
100 µm for ∆L/L~10-4, ~ 1.5 mm for ∆L/L~10-3
All by A.Stahl, old geometry [26,82] mrad, 3,05 m from IP
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
33
Conclusions on luminosity
measurement
x-secBhabha [nb]
σθ [mrad]
∆θ [mrad]
αres [GeV-1/2]
EBhabha [GeV]
Beam polarization
B/S
BS+ISR [%]
Mech. precision
Σ
Value
2.1
2.2 10-2
3.2 10-3
0.21
≥ 200
(0.8 e-, 0.6 e+)
2.3 10-3
12.8
(4µm, 100 µm)
Residual uncertainty
5.4 ⋅10-4 **
100% *
100% *
20%
2⋅10-3
2.5⋅10-3
100%*
0.36‰
-
∆L/L
5.4 ⋅10-4
1.6 ⋅10-4
1.6 ⋅10-4
1.0 ⋅10-4
1.0 ⋅10-3
1.9 ⋅10-4
2.3 ⋅10-3
3.6 ⋅10-4
1.0 ⋅10-4
2.6 10-3
* Upper limit – full size of the effect is taken as uncertainty.
** Uncertainty of the theoretical cross-section for Bhabha at LEP energies
[OPAL, G. Abiendi et al., Eur. Phys. J C14(2000)373].
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
34
Conclusions on luminosity
measurement
- Some of the systematic effects can be taken as corrections once their
experimental uncertainties are known (∆θ, miscounts due to physics
background).
-Detector related (∆θ, σθ, ∆α) and mechanical issues contribute to the
luminosity relative uncertainty ≤1‰.
- Physics background is the dominant effects, but it can be
suppressed at permille level at ILC energies (however, NLO corrections
has to be known to correct for it).
- Impact of the EM deflection has to be experimentally measured (of
particular importance for the low energy option (GigaZ).
Luminosity can be measured with the permille uncertainty at ILC energies
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
35
Reflects and prospects
In Serbian ☺
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
36
Pogled unazad
- Vinča institut je (za sada) jedina institucija iz Srbije koja učestvuje na
projektu budućeg linearnog kolajdera, od 2000 (2005).
- Iz te aktivnosti je proizašlo: nekoliko radova u vodećim časopisima,
oko 20 predavanja na medjuanarodnim skupovima, uključujući i
vodeće konferencije (LCWS, EPS HEP, ICHEP)
- 1 završena PhD teza i jedna u izradi
- Autorstvo na tehničkom dizajnu detektora za linearni kolajder (TESLA
TDR, ILC RDR, ILD LoI, CLIC CDR)
- MoC sa CERN, 2012
- MoU za CLIC CTF3, 2012
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
37
Perspektive
- Vinča Institut je dva puta bila domaćin FCAL skupova (2008 i 2011).
Učestvujemo u Programskom komitetu ECFA LC2013. Nadamo se
organizaciji LCWS 2014.
- Uključili smo se u CLIC Physics program sa temom identifikacije
Higgsovog bozona u procesu H→µµ na 350 GeV.
- Nadamo se saradnji sa Novim Sadom čije ćemo uključivanje u
kolaboracije FCAL i CLIC CTF3 podržati.
- Novi Sad je pozvan da se predstavi na FCAL Workshopu
(29. april -1. maj) 2013 u Krakowu.
- Verujemo da naša institucionalna saradnja može značajno da
doprinese klimi saradnje u fizici visokih energija u Srbiji.
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad
38
Hvala
10-Dec-2012
Ivanka Božović-Jelisavčić
PMF Novi Sad