Transcript TLEP3 parameters V0.2
TLEP: a first step on a long vision for HEP M. Koratzinos Univ. of Geneva On behalf of the TLEP study group Beijing, 16 August 2013
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2
A preamble
“…we chose these things not
because they are easy, but because they are hard, because that goal will serve to measure and organize the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one
which we intend to win”: J.F. Kennedy, president of the US, 1962 3
On challenges…
The ILC community has taken a formidable challenge and have managed to come with a solid design and TDR on what is a very tricky machine
but The Higgs is light and there is not yet any hint of new physics! So, the circular collider approach should be given a chance. It already promises better performance than an equivalent linear machine. We need to allow the circular approach to reach CDR level and compare.
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Contents
• • • • •
The physics case Circular collider challenges TLEP implementation TLEP physics reach TLEP design study
Acknowledgements: I am indebted to the whole TLEP community and especially R. Aleksan, A. Blondel, P. Janot, F. Zimmermann for liberal use of material This talk would not have been complete without the comparison data with the ILC. I hope I have represented them accurately 5
The physics case
• • • • • The energy scale of any new physics is already pushed to beyond a few hundreds of GeV and will probably be pushed to 1TeV or more with the next LHC run.
In this scenario, Physics beyond the standard model is only accessible via loop corrections rather than direct observation of a (heavy) state. The sensitivity of precision measurements can be to energy scales far above what is directly accessible in current or next generation machines (LHC, ILC, CLIC) A clearer picture on this will emerge after the next LHC run.
Meaningful over-constraining of the standard model can only start now that the Higgs sector is known and might lead to revealing weaknesses of the standard model 6
Precision needed
• Higgs couplings: sensitivity to new physics –
g g HXX
1 TeV 2 Typical deviations of SM Higgs couplings: with | NP d| < 5% • Where Λ 𝑁𝑃 is the energy scale for new physics (exact value of d depends on coupling and model) Need at least a per-cent accuracy for a 5s observation if Λ NP per-cent accuracy for multi-TeV New Physics scale = 1 TeV and a sub • • • Z pole measurements – Increase sensitivity to new physics by an order of magnitude smaller errors 10,000 more statistics need 100 times W and top mass determination – Need to match the precision of direct measurements by improving by one order of magnitude (It is not clear that the ILC can deliver these accuracies) 7
Circular colliders
• • •
In the next few slides I would like to overview the parameters that affect circular collider performance. I will then show what can reasonably be achieved in terms of luminosity.
The following is not TLEP specific; it can apply to any circular machine (CEPC?)
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Major limitations
•
The major limitations of circular colliders are:
– Power consumption luminosity limitations that affect the – Tunnel size limitations that affect the luminosity and the energy reach – Beam-beam effect limitations that affect the luminosity – Beamstrahlung lifetimes limitations that affect (and ultimately luminosity ) beam 9
Energy reach
• • In a circular collider the energy reach is a very steep function of the bending radius. To make a more quantitative plot, I have used the following assumptions: – – RF gradient: 20MV/m Dipole fill factor: 90% (LEP was 87%) I then plot the energy reach for a specific ratio of RF system length to the total length of the arcs 𝐸 𝑙𝑜𝑠𝑠 [𝐺𝑒𝑉] = 8.85 × 10 −5 𝐸 4 𝑟 𝑏𝑒𝑛𝑑 and 𝐿 𝑅𝐹 [𝑚] = 𝐸 𝑙𝑜𝑠𝑠 20𝑀𝑒𝑉 10
14000 12000 10000 8000 6000 4000 2000 0 100
Energy reach
Energy reach
5% RF 2% RF 1% RF Assumptions: 20mV/m, 90% dipole fill factor.
What is plotted is the ratio of RF length to total arc length 150 200 250
beam energy (Gev)
300 350 LEP2 had a ratio of RF to total arc length of 2.2% TLEP175 sits comfortably below the 1% line 11
Luminosity of a circular collider
Luminosity of a circular collider is given by ℒ = 𝑓 𝑟𝑒𝑣 𝑛 𝑏 𝑁 𝑏 2 4𝜋𝜎 𝑥 𝜎 𝑦 𝑅 ℎ𝑔 Which can be transformed in terms of 𝑟 𝑒 𝛽 𝑦 ∗ 𝜉 𝑦 = 𝑁 𝑏 2𝜋𝛾𝜎 𝑥 𝜎 𝑦 and 𝑃 𝑙𝑜𝑠𝑠,𝑡𝑜𝑡𝑎𝑙 = 4𝜋 3 𝑟 𝑒 𝑚 𝑒 3 𝐸 4 𝑓 𝑟𝑒𝑣 𝑛 𝑏 𝑁 𝑏 𝜌 to: 12
Luminosity of a circular collider
ℒ = 3 8𝜋 𝑚 𝑒 𝑟 𝑒 𝑐 2 2 2 𝑃 𝑡𝑜𝑡 𝜌 𝐸 0 3 𝜉 𝑦 𝑅 ℎ𝑔 𝛽 𝑦 ∗
The maximum luminosity is bound by the
total power dissipated
, the maximum achievable
beam-beam parameter
(the beam-beam limit),
the bending radius, the beam energy
,
𝛽 𝑦 ∗
, and the
hourglass effect
(which is a function of
σ z
and
𝛽 𝑦 ∗
)
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Total power
• • •
Luminosity is directly proportional to the total power loss of the machine due to synchrotron radiation.
In our approach, it is the first parameter we fix in the design (the highest reasonable value) Power loss is fixed at 100MW for both beams (50MW per beam)
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Machine radius
• • •
The bending radius of the collider also enters linearly in the luminosity formula The higher the dipole filling factor, the higher the performance [there is a small dependance on the maximum beam-beam parameter since smaller machines for the same beam energy can achieve higher beam-beam parameters]
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Beam-beam parameter
The maximum beam-beam parameter is a function of the damping decrement: ξ 𝑦 𝑚𝑎𝑥 = 𝑓(𝜆 𝑑 ) where 1 𝜆 𝑑 = 𝑓 𝑟𝑒𝑣 𝜏 𝑛 𝐼𝑃 Or, more conveniently: 𝜆 𝑑 = one IP to the next.
𝑈 𝐸 0 𝑛 1 𝐼𝑃 𝑜𝑟 𝜆 𝑑 ∝ 𝐸 0 𝜌 𝑛 3 𝐼𝑃 The damping decrement is the fractional energy loss from Therefore, for a specific machine, generally higher than for 2IPs ξ 𝑦 𝑚𝑎𝑥 for 1IP is 16
Maximum beam-beam
• • • • • It is not trivial to predict what can be achieved in terms of beam-beam parameter at TLEP or other machines. LEP is a good yardstick to use LEP achieved ξ 𝑦 𝑚𝑎𝑥 = 0.045
at 45GeV and run up to 0.08 at 100GeV without reaching the beam-beam limit Going up in energy increases the damping decrement (and therefore ξ 𝑦 𝑚𝑎𝑥 ) Values between 0.05 and 0.1
possible should be achievable with relative ease at future circular colliders. At beam energies of 120GeV or higher, higher values might be 17
Beta* and hourglass
We are opting for a realistic β* y value of 1mm. σ beam sizes vary from 1mm to 3mm. In this range the hourglass effect is between 0.9 to 0.6
z
R for beta*_y of 1mm
1 0,9 0,8 0,7 Self-consistent σ z at different energies for TLEP 0,6 0,5 0,4 0,3 0,5 1 1,5 2 2,5
sigma_z (mm)
3 3,5 4 4,5 18
Luminosity of a circular collider
1,00E+36 1,00E+35 1,00E+34 Single IP luminosity of a circular collider • • • • of 9000m bending radius as a function of beam energy. Power loss is 100MW. ξy between 0.05 and 0.1. β* y = 1mm. 𝑅 ℎ𝑔 =0.75
1,00E+33 0 50 100 150
beam energy [GeV]
200 250 19
Beamstrahlung
• • • • Beamstrahlung is the interaction of an incoming electron with the collective electomagnetic field of the opposite bunch at an interaction point.
Main effect at circular colliders is a single hard photon exchange taking the electron out of the momentum acceptance of the machine.
If too many electrons are lost, beam lifetime is affected [the beamstrahlung effect at linear colliders is much larger and it increases the beam energy spread] 20
Beamstrahlung (2)
• • • • The beamstrahlung limitation was introduced by Telnov* It depends on 𝜂 𝜎 𝑥 𝜎 𝑧 acceptance, 𝜎 𝑥 𝜎 𝑧 𝑁 𝑏 where 𝜂 is the momentum the beam sizes in x and z (note no 𝜎 𝑦 dependence!) and 𝑁 𝑏 per bunch is the number of electrons It has a γ 2 dependence, so it is only important at high energies (>~120GeV per beam) It is mitigated by high momentum acceptance, small emittances and very flat beams
Comparison with simulation
The Telnov formula was checked against a realistic simulation (Guineapig – courtesy the ILC) at different energies [work of M. Zanetti] and found to be pessimistic
TLEP-t comparison TLEP-H comparison
1000,00 1000,00 100,00 10,00 100,00 TLEP-t Telnov Telnov tuned TLEP-t GuineaPig 10,00 TLEP-H Telnov Telnov tuned TLEP-H GuineaPig 1,00 0,015 0,02 0,025
momentum acceptance
0,03 1,00 0,015 0,02 0,025
momentum acceptance
0,03 The ‘tuned’ model corresponds to an ad hoc tuning of the Telnov formula to fit the data better: instead of 10% of the electrons seeing a 100% field, 100% of electrons see a 70% field 22
1,00E+05
Beamstrahlung limitation
1,00E+04 1,00E+03 1,00E+02 1,00E+01 Telnov Telnov tuned Plot on left is if we run with a value of the beam-beam parameter of 0.1
Above ~180 GeV is difficult to run without opting for a more modest beam-beam parameter value (which would reduce the luminosity) 1,00E+00 100 120 140 160
beam energy (GeV)
180 TLEP Latest parameter set, mom. acceptance 2.2% 200 Can even run at 250GeV with a beam-beam parameter of 0.05
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A specific implementation: TLEP
• • • • A study has been commissioned for an 80-km tunnel in the Geneva area.
For TLEP we fix the radius (conservatively 9000m) the power (100MW) and try to have beams as flat at possible to reduce beamstrahlung. Our arc optics design (work in progress) conservatively uses a cell length of 50m, which still gives a horizontal emittance of 2nm at 120GeV We assume that we can achieve a horizontal to vertical emittance ratio of 500-1000 (LEP was 200) LHC Possible TLEP location 24
Other tunnel diameters
• • • …but of course other tunnel diameters and locations are equally good Many other proposals floating, but I would like to mention the Circular Electron-Positron Collider in China (CEPC) – certainly the tunnel can be built more cheaply in China Performance scales with tunnel size, but in case no funds are available for a new tunnel, the LHC tunnel can be used after the end of the LHC physics programme (a project we call LEP3) 25
TLEP implementation
At 350 GeV, beams lose 9 GeV / turn by synchrotron radiation
Need 600 5-cell SC cavities @ 20 MV/m in CW mode
Much less than ILC (8000 9-cell cavities@ 31 MV/m)
Length ~900 m, similar to LEP (7 MV/m)
200 kW/ cavity in CW : RF couplers are challenging
BNL 5-cell 700 MHz cavity
Heat extraction, shielding against radiation, … Luminosity is achieved with small vertical beam size :
s
y
~ 100 nm A factor 30 smaller than at LEP2, but much more relaxed than ILC (6-8 nm)
TLEP can deliver 1.3 × 10 34 cm -2 s -1 per collision point at √s = 350 GeV Small beam lifetime due to Bhabha scattering ~ 15 minutes
Need efficient top-up injection
RF Coupler (ESS/SPL) A. Blondel F. Zimmermann Patrick Janot 26
SuperKEKB: a TLEP demonstrator
• • SuperKEKB will be a TLEP demonstrator • Beam commissioning starts early 2015 Some SuperKEKB parameters : – – – – Lifetime : 5 minutes • • b * y TLEP : 15 minutes : 300 m m TLEP : 1 mm s y • : 50 nm TLEP : ~100 nm e y / e x • : 0.25% TLEP : 0.20%-0.10% – Positron production rate : 2.5 × 10 12 / s • TLEP : < 1 × 10 11 / s – Off-momentum acceptance at IP : ±1.5% • TLEP : ±2.0 to ±2.5% 27
TLEP Cost (Very Preliminary) Estimate
Cost in billion CHF
Bare tunnel Services & Additional infrastructure (electricity, cooling, service cavern, RP, ventilation, access roads …) RF system
3.1 (1) 1.0
(2) 0.9 (3)
Cryo system Vacuum system & RP Magnet system for collider & injector ring Pre-injector complex SPS reinforcements
0.2
(4) 0.5
(5) 0.8
(6) 0.5
Total
(1): J. Osborne, Amrup study, June 2012 (2): Extrapolation from LEP (3): O. Brunner, detailed estimate, 7 May 2013
7.0
Cost for the 80 km version : the 100 km version might be cheaper.)
As a self-standing project : Same order of magnitude as LHC As an add-on to the VHE-LHC project : Very cost-effective : about 2-3 billion CHF
Note: detector costs not included – count 0.5 per detector (LHC)
Cost per Higgs boson : 1 - 3 kCHF / Higgs (ILC cost : 150 k$ / Higgs) [ NB : 1CHF ~ 1$ ] LEP/LHC
(4): F. Haug, 4 th TLEP Days, 5 April 2013
80-100 km tunnel
(5): K. Oide : factor 2.5 higher than KEK, estimated for 80 km ring (6): 24,000 magnets for collider & injector; cost per magnet 30 kCHF (LHeC); Patrick Janot 28
Power consumption
Highest consumer is RF:
RF systems cryogenics top-up ring Total RF TLEP 120 TLEP 175
173-185 MW 10 MW 34 MW 3 MW 186-198 MW 5 MW 212-224 MW Limited by Klystron CW efficiency of 65%. This is NOT aggressive and we hope to be able to do better after dedicated R&D Total power consumption for 350GeV running:
Power consumption RF including cryogenics cooling ventilation magnet systems general services Total TLEP 175
224MW 5MW 21MW 14MW 20MW ~280MW • • CERN 2010 power demand: Full operation 220MW Winter shutdown 50MW 29 IPAC13 TUPME040,
arXiv:1305.6498
[physics.acc-ph]
A note on power consumption
• • • • TLEP is using ~280MW while in operation and probably ~80MW between physics fills. So for 1×10 7 sec of operation and 1×10 7 sec of stand-by mode, total electricity consumption is ~1TWh CERN is currently paying ~50CHF/MWh TLEP yearly operation corresponds to ~50MHF/year This should be seen in the context of the total project cost (less than 1% of the total cost of the project goes per year to electricity consumption) 30
TLEP parameter set
TLEP Z TLEP W TLEP H TLEP t E beam [GeV] circumf. [km] beam current [mA] #bunches/beam #e − /beam [10 12 ] horiz. emit. [nm] vert. emit. [nm] bending rad. [km] κ ε mom. c. α c [10 −5 ] P loss,SR /beam [MW] β
∗
x [m] β
∗
y [cm] σ
∗
x [μm] σ
∗
y [μm] hourglass F hg E SR loss /turn [GeV] V RF ,tot [GV] d max,RF ξ x /IP [%] ξ y /IP f s [kHz] E acc [MV/m] eff. RF length [m] f RF [MHz] δ SR rms [%] σ SR z,rms [cm]
ℒ
/IP[10 32 cm −2 s −1 ] number of IPs beam lifet. [min]
440 9.0
50 0.5
0.1
124 0.27
0.71
45 80 1180 4400 1960 30.8
0.07
9.0
0.04
2 4.0
0.07
0.07
1.29
3 600 700 0.06
0.19
5600 4 67 175 80 5.4
12 9.0
10 0.01
9.0
1000 1.0
50 1 0.1
100 0.10
0.65
9.2
12 4.9
0.10
0.10
0.43
20 600 700 0.22
0.25
130 4 20 470 1.0
50 0.5
0.1
68 0.14
0.75
120 80 24.3
80 40.8
9.4
0.02
9.0
2.0
6 9.4
0.10
0.10
0.44
10 600 700 0.15
0.17
480 4 16 80 80 124 600 200 9.4
0.02
9.0
470 2.0
50 0.5
0.1
78 0.14
0.75
0.4
2 5.5
0.10
0.10
0.45
3 600 700 0.10
0.22
1600 4 25 IPAC13 TUPME040,
arXiv:1305.6498
[physics.acc-ph]
Too pessimistic! 2nm @120GeV or lower should he easy By definition, in a project like TLEP, from the moment a set of parameters is published it becomes obsolete and we now already have an improved set of parameters.
The new parameter set contains improvements to our understanding, but does not change the big picture.
Revised (taking into account BS) but similar 31
Luminosity of TLEP
Z, 2.10
36 TLEP : Instantaneous lumi at each IP (for 4 IP’s) Instantaneous lumi summed over 4 IP’s WW, 6.10
35 HZ, 2.10
35 tt , 5.10
34 • • Why do we always quote 4 interaction points?
It is easier to extrapolate luminosity from the LEP experience. Lumi of 2IPs is larger than half the lumi of 4IPs According to a particle physicist: “give me an experimental cavern and I guarantee you that it will be filled” 32
Upgrade path
• • TLEP offers the unique possibility to be followed by a 100TeV pp collider (VHE-LHC) Luminosity upgrade: a study will be launched to investigate if luminosity can be increased by a significant factor at high energies (240 and 250GeV E CM ) by using a charge-compensated scheme of four colliding beams. We will aim to gain a factor of 10 (to be studied and verified) 33
TLEP : Possible Physics Programme
Higgs Factory mode at √s = 240 GeV: 5+ years
Higgs boson properties, WW and ZZ production.
Periodic returns at the Z peak for detector and beam energy calibration
Top Threshold scan at √s ~ 350 GeV: 5+ years
Top quark mass, width, Yukawa coupling; top quark physics; more Higgs boson studies.
Periodic returns at the Z peak for detector and beam energy calibration Z resonance scan at √s ~ 91 GeV: 1-2 years
Get 10 12 Z decays @ 15 kHz/IP. Repeat the LEP1 Physics Programme every 15 minutes.
Continuous transverse polarization of some bunches for precise E beam calibration WW threshold scan at √s ~ 161 GeV: 1-2 years
Get 10 8 W decays; Measure the W mass; Precise W studies.
Continuous transverse polarization of some bunches and returns to the Z peak.
Longitudinally polarized beams at √s = m Z : 1 year
Get 10 11 Z decays, and measure A LR , A FB pol , etc.
Polarization wigglers, spin rotators Luminosity, Energy, Polarization upgrades
If justified by scientific arguments (with respect to the upgrade to VHE-LHC)
Patrick Janot 34
TLEP as a Mega-Higgs Factory (1)
Unpolarized cross sections PJ and G. Ganis
Z
→ All
Z
→ nn Patrick Janot
Lumi / 5 yrs Beam Polarization # of HZ events # of WW
→
H events
ILC-250 250 fb -1 80%, 30% 70,000 3,000
TLEP-240 10 ab
-1
– 2,000,000 50,000
ILC-350 350 fb -1 80%,30% 65,000 20,000
TLEP-350 2.6 ab
-1
– 325,000 65,000
35
TLEP as a Mega-Higgs Factory (2)
e
Example : e
e
-
→
Measure
s
HZ ZH → l
l
-
+ anything
e H
Summary of the possible measurements : (TLEP : CMS Full Simulation + some extrapolations for cc, gg)
Z* ILC TDR From P. Azzi et al.
arXiV:1208.1662
+
g HZZ
Z e , m e , m TLEP-240 1 year 1 detector s
HZ
s
HZ * BR(H → bb)
s
HZ * BR(H → cc)
s
HZ * BR(H → gg)
s
HZ * BR(H → WW)
s
HZ * BR(H →
tt
)
s
HZ * BR(H → ZZ)
s
HZ * BR(H →
gg
)
s
HZ * BR(H →
mm
)
G
INV /
G
H m H ILC-250 2.5% 1.1% 7.4% 9.1% 6.4% 4.2% 19% 35% 100% < 1% 40 MeV TLEP-240 0.4% 0.2% 1.2% 1.4% 0.9% 0.8% 3.1% 3.0% 13% < 0.2% 8 MeV
Patrick Janot 36
Global fit of the Higgs couplings
Model-independent fit Coupling LEP-240 g Z 0.16% g W 0.85% g b 0.88% LEP-350 ILC-350 0.15% 0.9% 0.19% 0.5% 0.42% 2.4% g c 1.0% 0.71% 3.8% g g 1.1% 0.80% 4.4% g
t
0.94% 0.54% 2.9% g
m
6.4% 6.2% 45% g
g
1.7% 1.5% 14.5%
M. Bachtis
BR exo 0.48% 0.45% 2.9%
1.0% ± 1%
NB : Theory uncertainties must be worked out.
Patrick Janot Snowmass 2013 37
TLEP as a Mega-Top Factory
-
Scanning the tt threshold at √s ~ 350 GeV
Effect of beamstrahlung on E_beam at TLEP is small compared to Linear Colliders Luminosity E Spectrum Effect on top threshold
M. Zanetti
TLEP, TLEP ILC
No need to measure the luminosity spectrum @ TLEP reduced m top uncertainty Slightly larger cross section @ TLEP
Beam energy calibration from e + e → WW and m W ; a s from Z and W leptonic decays.
Still need to work on theoretical predictions (40 MeV uncertainty on m top ) Expected sensitivity for TLEP (full study to be done) and ILC Lumi / 5 years # top pairs
D
m top
DG
top
Dl
top /
l
top TLEP 4 × 650 fb -1 1,000,000 10 MeV 12 MeV 13%
ILC 350 fb -1 100,000 30 MeV 35 MeV 40% Stat. only Patrick Janot 38
TLEP as a Tera-Z and Oku-W Factory (1)
TLEP repeats the LEP1 physics programme every 15 minutes
Added value: Transverse polarization up to the WW threshold (LEP: up to 60GeV)
Exquisite beam energy determination with resonant depolarization
Up to 5 keV precision – unique at circular e
e
-
colliders Measure m Z , m W ,
G
Z , … with unbeatable accuracy
Z lineshape, asymetries WW threshold scan New Physics in loops ?
Measure the number of neutrinos
From the peak cross section at the Z pole – Luminosity measurement is a challenge From radiative returns to the Z from the WW threshold – e+e →
gnn Patrick Janot No beamstrahlung is a clear advantage 39
TLEP as a Tera-Z and Oku-W Factory (2)
This is a unique part of the TLEP programme (that was not covered by the snowmass reports yesterday). It is also very challenging for the accelerator (intensity, longitudinal polarization), experiments (rate) and Theory
Measurements with Tera-Z Caution : TLEP will have 5×10 4 more Zs than LEP times smaller statistical precision is difficult Predicting achievable accuracies with 250 The study is just beginning : errors might get better with increasing understanding Much more to do at the Z peak e.g., asymmetries, flavour physics (>10 11 b, > 10 11 rare Z decays, … c, > 10 10 t), Measurements with Oku-W Caution : TLEP will have 5×10 6 more W than LEP at the WW threshold Predicting achievable accuracies with 1000 times smaller statistical precision is difficult Much more W physics to do at the WW threshold and above e.g., G W , l W , rare W decays, diboson couplings, … Measurement with longitudinal polarization One year data taking with luminosity reduced to 20% of nominal (requires spin rotators) 40% beam longitudinal polarization assumed – NB: LEP kept polarization in collisions -
hardware needed is challenging
NB: ILC limited to a factor > 30 larger errors 40
EWSB Precision tests at TLEP: Teaser
lkjfs Warning : indicative only.
Complete study being done ILC TLEP TLEP
Patrick Janot
Very stringent SM closure test.
Sensitivity to weakly-interacting BSM Physics at a scale > 10 TeV
41
TLEP Design Study: Structure
26 Working Groups: Accelerator / Experiment / Phenomenology
42
TLEP Design Study: People
• 296 295 subscribers from 23 countries (+CERN) – Distribution reflects the level of awareness in the different countries • 4 physicists from China: subscribe at
http://tlep.web.cern.ch
!
43
Watch this space
• http://tlep.web.cern.ch
• • Next event : Sixth TLEP workshop 16-18 October 2013 http://indico.cern.ch/conferenceDisplay.py?ovw=True&confId=25771 Joint VHE-LHC + TLEP kick-off meeting in February 2014 44
Conclusions
• • TLEP is a 3-in-1 package: – It is a powerful Higgs factory – It is a high-intensity EW parameter buster – It offers the path to a 100TeV pp collider TLEP is based on solid technology and offers little risk, has a price tag which is expensive but not out of reach, has reasonable consumption, offers multiple interaction points and might even have an upgrade potential.
45
Concluding remarks
Z 0 GeV
OR
GeV upgrades and performance improvements from both sides 46
THANK YOU
end 47
Extra slides
48
Beamstrahlung
• • • • I am using the approach of Telnov throughout* The energy spectrum of emitted photons during a collision of two intense bunches (usual bremstrahlung formula) is characterized by a critical energy 𝐸 𝑐 = ħ3γ 0 2ρ 3 𝑐 Where ρ is the radius of curvature of the affected electron which depends on the field he sees ρ = γ 0 𝑚𝑐 2 𝑒𝐵 And the maximum field can be approximated by 𝐵 𝑚𝑎𝑥 = 2𝑒𝑁 𝑏 𝜎 𝑥 𝜎 𝑧
Beamstrahlung
•
So, the critical energy turns out to be
constants 3𝑟 𝑒 2 γ 0 𝑁 𝑏 𝐸 𝑐 = 𝐸 0 α𝜎 𝑥 𝜎 𝑧
for the maximum field (it would be smaller for a smaller field) Telnov’s approximation:
• 10% of electrons see maximum field • 90% of electrons see zero field 50
Beamstrahlung
• • • • • Electrons are lost if they emit a gamma with an energy larger than the momentum acceptance, η: 𝐸 𝛾 ≥ 𝜂𝐸 0 We define 𝑢 = 𝜂 𝐸 0 or otherwise 𝑢 = 𝐸 𝑐 The number of photons with 𝐸 𝛾 ≥ 𝜂𝐸 𝛼 3𝛾𝑟 𝑒 2 0 ∶ 𝜂 𝜎 𝑥 𝜎 𝑧 𝑁 𝑏 𝑛 𝛾 = 𝛼 2 6𝜋𝑟 𝑒 𝜂 𝛾 𝜎 𝑧 2 𝑢 3 2 𝑒 − 𝑢 So we see that η can directly be traded off by 𝑁 𝑏 𝜎 𝑥 𝜎 𝑧 Going up in energy aggravates the effect 51
Beamstrahlung energy dependence
• • •
For a specific ring, power consumption, emittances and ξ: Number of particles per bunch scales with gamma:
𝑁 𝑏 = 𝜉 𝑦 2𝜋𝛾𝜎 𝑥 𝜎 𝑦 𝑟 𝑒 𝛽 ∗ 𝑦
And
u scales with γ 2
. This produces a steep drop in lifetime with increased energy
52
European Strategy recommendations
High-priority large-scale scientific activities – Second-highest priority, recommendation #2
physics results from the LHC running at 14 TeV will be available.
CERN should undertake design studies for accelerator projects in a global context, with emphasis on proton-proton and electron-positron high-energy frontier machines. These design studies should be coupled to a vigorous accelerator R&D programme, including high-field magnets and high-gradient accelerating structures, in collaboration with national institutes, laboratories and universities worldwide.
The two most promising lines of development towards the new high energy frontier after the LHC are proton-proton and electron-positron
•
colliders . Focused design studies are required in both fields, together with vigorous accelerator
Excerpt from the CERN Council deliberation document (22-Mar-2013)
universities and laboratories worldwide. The Compact Linear Collider (CLIC) is an electron-positron machine based on a novel two-beam acceleration technique, which could, in stages, reach a centre-of-mass energy up to 3 TeV. A Conceptual Design Report for CLIC has already been prepared. Possible proton-proton machines of higher energy than the LHC include HE-LHC , roughly doubling the centre-of-mass energy in the present tunnel, and VHE-LHC , aimed at reaching up to 100 TeV in a new circular 80km tunnel . A large tunnel such as this could also host a circular e
e
-
machine (TLEP) reaching energies up to 350 GeV with high luminosity.
53
CERN medium term plan
54
The TLEP tunnel
• • • • • Standard size tunnel boring machines dictate a larger tunnel size of 5.6m diameter (LHC: 3.8m) Maximize boring in ‘molasse’ (soft stone) 80km design necessitates a bypass tunnel to avoid very deep shafts at points 4 and 5 A larger tunnel might actually be cheaper This is only the beginning of the geological study 55
Global fit of the Higgs couplings (2)
Model-dependent (seven-parameter) fit a-la-LHC
Assume no exotic Higgs decays, and
k
c =
k
t
HL-LHC : One experiment only … CMS Scenario 1 CMS Scenario 2 CMS, July 13 ± 1% (HL-LHC : One experiment only)
In bold, theory uncertainty are assumed to be divided by a factor 2, experimental uncertainties are assumed to scale with 1/√L, and analysis performance are assumed to be identical as today
Quantitative added value from ILC – wrt HL-LHC – does not stick out clearly.
In contrast, sub-per-cent TLEP potential is striking for all couplings
Only TLEP is sensitive to (multi-)TeV new physics with Higgs measurements Much theoretical progress is needed to reduce accordingly theory uncertainties
Patrick Janot 56
TLEP as a Mega-Higgs Factory (3)
Determination of the total width
From the number of HZ events and of ZZZ events at √s = 240 GeV
G
H
= G (
H
®
ZZ
) / BR(
H
®
ZZ
) µ s
HZ
/ BR(
H
®
ZZ
)
From the bb
nn
final state at √s = 350 GeV (and 240 GeV)
G
H
µ G (
H
®
WW
) / BR(
H
®
WW
) µ s
WW
®
H
®
bb
/ BR(
H
n ®
WW
) ´ BR(
H
®
bb
) n G
H from:
HZ
→ ZZZ @ 240 WW → H @240 WW → H @350 ILC 20% 12% 7% TLEP 3.2% 2.4% 1.2% Combined 5.8%
Note : mm DG H / G H collider ~ 5%
1.0%
Patrick Janot 57
Higgs Physics with √s > 350 GeV ? (1) Signal cross sections in e
e
-
collisions
+
H H
Measurements at higher energy
√s > 350 GeV does not do much for couplings to c, b, g, Z, W,
g
,
m
and
G
tot . (slide 15)
Invisible width best done at √s = 240 GeV
The ttH coupling benefits from higher energy
TLEP 350 : 13% ILC 500 : 14% ; ILC 1 TeV : ~4% ; CLIC : ~4% The HL-LHC will already do the measurement with 5% precision (and improving)
Sub-per-cent precision will need the ultimate pp machine at 100 TeV : VHE-LHC
Patrick Janot 58
Higgs Physics with √s > 350 GeV ? (2)
Measurements at higher energy (cont’d)
Higgs tri-linear self coupling
l
very difficult for all machines Particularly difficult for √s < 2-3 TeV Few per-cent precision will need VHE-LHC
± 20% J. Wells et al.
arXiV:1305.6397
Snowmass, Aug 13
ILC500 , HL-LHC
0.5 ab -1 3 ab -1
ILC1TeV , HE-LHC
1 ab -1 3 ab -1
CLIC3TeV , VHE-LHC
2 ab -1 3 ab -1
Summary
For the study of H(126), the case for e
e
-
collisions above 350 GeV is not compelling.
A stronger motivation will exist if a new particle found (or inferrred) at LHC
IF e
e
-
collisions can bring substantial new information about it
Patrick Janot 59
Quantity
EW parameter summary
Physics Present precision TLEP Stat errors Possible TLEP Syst. Errors TLEP key Alain Blondel, Snowmass on Minnesota, 2 August 2013 M Z
( keV)
Input
91187500 2100 G
R N N
l
Z
n n (keV) D
(T) (no
D
!)
s ,
d
b PMNS Unitarity sterile
n
’s PMNS Unitarity sterile
n
’s
2495200 2300 20.767 0.025
2.984 0.008
2.92 0.05
R b
d
b
0.21629 0.00066
A M LR W
MeV/c2
m top
MeV/c2 D
,
e
3 ,
D
(T, S )
D
,
e
3 ,
e
2, (T, S, U)
D
Input
0.1514
80385 ± ± 0.0022
15 173200 900 Z Line shape scan
5 keV
Z Line shape scan
8 keV
Z Peak Z Peak ( g +Z_inv) ( g +Z ll ) Z Peak Z peak, polarized Threshold (161 GeV) Threshold scan
0.0001
0.00008
0.001
(161 GeV)
<0.001
0.000003
0.000015
0.3 MeV 10 MeV <100 keV <100 keV <0.001
<0.004 <0.000060
<0.000015
<0.5 MeV <10MeV
E_cal E_cal Statistics
Challenge
QED corrections QED corrections Statistics QED corrections
Bhabha scat.
Statistics , small IP 4 bunch scheme, > 2exp E_cal & Statistics Hemisphere correlations Design experiment QED corections E_cal & Statistics 40MeV?