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Journees CMS France, 29 - 31 Mars 2006 Mont Sainte Odile, Alsace. Physics potential of a luminosity upgraded LHC (SLHC at ~10 35 cm -2 s -1 ) D. Denegri , CE Saclay/DAPNIA/SPP. aspects discussed: - machine - detectors

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Journees CMS France, 29 - 31 Mars 2006

Mont Sainte Odile, Alsace

Physics potential of a luminosity upgraded LHC

(SLHC at ~1035 cm-2 s-1)

D. Denegri,


aspects discussed:

- machine

- detectors

- physics

probable possible lhc luminosity profile longer term

Z’ ~ 6TeV

ADD [email protected]

[email protected]


[email protected]



[email protected]

[email protected]


200 fb-1/yr




100 fb-1/yr

1000 fb-1/yr

First physics run: O(1fb-1)

Probable/possible LHC luminosity profile - longer term

L = 1033

L = 1034

SLHC: L = 1035

physics potential of the lhc at 10 35 cm 2 s 1 slhc
Physics potential of the LHC at 1035 cm-2 s-1 (SLHC)

What improvements in the physics reachoperating theLHC at aluminosity of

~ 1035 cm-2 s-1 with an integrated luminosity ~ 1000 fb-1per year at √s ≈ 14 TeV i.e. retaining present LHC magnets/dipoles -

an upgrade at a relatively modest cost for machine + experiments

(< 0.5 GSF) for ~ 2013-15

a more ambitious upgrade (but ~ 2-3 GSF!) would be to go for a √s ≈ 30 TeV

machine changing LHC dipoles (~16T, Nb3Sn?) - not discussed here

- expected modifications/adaptations of LHC and experiments/CMS,

- improvements in some basic SM measurementsand inSM/MSSM Higgs reach

- improvements inreach at high mass scales, main motivations for an upgrade i.e exploit maximally the “existing” machine and detectors

nominal lhc and possible upgrades
Nominal LHC and possible upgrades

Nominal LHC: 7 TeV beams,

- injection energy: 450 GeV, ~ 2800 bunches, spacing 7.5 m (25ns)

- 1.1 *1011 protons per bunch, b* at IP : 0.5 m  1034 cm-2 s-1 (lumi-lifetime 10h)

Possible upgrades/steps considered:

-increase up to 1.7 *1011 protons per bunch (beam-beam limit)  2*1034 cm-2 s-1

- increase operating field from 8.3T to 9T (ultimate field)  √s ≈ 15 TeV

minor hardware changes to LHC insertions or injectors:

- modify insertion quadrupoles (larger aperture) for b* = 0.5  0.25 m

- increase crossing angle 300 mrad  424 mrad

- halving bunch spacing (12.5 nsec), with new RF system

 L ≈ 5 *1034 cm-2 s-1

major hardware changes in arcs or injectors:

- SPS equipped with superconducting magnets to inject at ≈ 1 TeV  L ≈ 1035 cm-2 s-1

- new superconducting dipoles at B ≈ 16 Tesla for beam energy ≈ 14TeV i.e.√s ≈ 28 TeV

nominal lhc and possible upgrades ii
Nominal LHC and possible upgrades (II)
  • increase operating field from 8.3T to 9T
  • (ultimate field)
  •  √s ≈ 15 TeV

major hardware changes in arcs or injectors:

- SPS equipped with superconducting magnets

to inject at ≈ 1 TeV

 Luminosity increase by factor ≈ 2

- new superconducting dipoles at B ≈ 16 Tesla

(Nb3Sn?) for beam energy ≈ 14TeV i.e.

√s ≈ 28 TeV

Last step would be very expensive…2 - 3 GSF.

shielding between machine and hf
Shielding between machine and HF

Basic functions of the shielding elements between the machine area and HF are:

-reduce the neutron flux in the cavern by 3 orders of magnitude

-reduce the background rate in the outer muon spectrometer (MB4, ME3,ME4) by

3 orders of magnitude

-reduce the radiation level at the HF readout boxes to a tolerable level


Rotating system is near the limits of mechanical strength,new concept or supplementary system

around existing RS needed for SLHC running,

time needed to open and close CMS would increase significantly (~1 week per shutdown)

cms longitudinal view modifications considered for slhc yoke and forward
CMS longitudinal view/ modifications considered for SLHC - yoke and forward

End cap yoke for SLHC, muon

acceptance up to |h ~ 2

Reinforced shielding inside

forward muons, replacement

of inner CSC and RPC’s

Supplement YE4 wall with

borated polythene

Improve shielding of HF PMT’s

Possibly increase YE1-YE2 separation to insert another detector layer?

experimental conditions at 10 35 cm 2 s 1 12 5ns considerations for tracker and calorimetry
Experimental conditions at 1035 cm-2 s-1 (12.5ns) - considerations for tracker and calorimetry

~ 100 pile-up events per bunch crossing - if 12.5 nsec bunch spacing (with adequate/faster electronics, reduced integration time) -

compared to ~ 20 for operation at 1034cm-2s-1 and 25 nsec (nominal LHC regime),

dnch/dh/crossing ≈ 600 and ≈ 3000 tracks in tracker acceptance

H  ZZ  eemm, mH = 300 GeV, in CMS

Generated tracks, pt > 1 GeV/c cut, i.e. all soft tracks removed!

I. Osborne



If same granularity and integration time as now: tracker occupancy and radiation dose in central detectors increases by factor ~10, pile-up noise in calorimeters by ~ 3 relative to 1034

inner cmstracking for slhc
Inner CMStracking for SLHC

From R.Horisberger

  • Pixels to much larger radius
  • Technology and Pixel size vary with radius
  • Not too large an extrapolation in sensor technology
  • Cost/Geometry optimization
foreseeable changes overview to detectors for 10 35 cm 2 s 1
Foreseeable changes (overview)to detectors for 1035cm-2s-1
  • changes to CMS and ATLAS :
  • Trackers, to be replaceddue to increased occupancy

to maintain performance, need improved radiation

hardness for sensors and electronics

- present Si-strip technology is OK at R > 60 cm

- present pixel technology is OK for the region ~ 20 < R < 60 cm

- at smaller radii(<10cm) new techniques required

  • Calorimeters: ~ OK

- endcap HCAL scintillators in CMS to be changed

- endcap ECAL VPT’s and electronics may not be

enough radiation hard

- desirable to improve granularity of very

forward calorimeters - for jet tagging

  • Muon systems: ~ OK

- acceptance reduced to |h| <~ 2.0

to reinforce forward shielding

  • Trigger(L1), largely to be replaced,

L1(trig.elec. and processor)

for 80 MHz data sampling

VF calorimeter for “jet tagging”


Compact NbTi quadrupoles, 70 mm aperture

To be inserted in CMS and ATLAS to reduce L*

With iron 160 T/m – Φ 250 mm

Φ 340 mm including cryostat

No stray field outside cold mass

Saturated iron 145 T/m – Φ 160 mm

Φ 250 mm including cryostat

Stray field outside cold mass

80 mm

cold mass

125 mm

cold mass

For higher gradients (200 T/m with NbTi – 275 T/m with Nb3Sn) cryostat dimensions will increase beyond 400 mm

forward jet tagging at 10 35 cm 2 s 1
Forward jet tagging at 1035 cm-2 s-1

Fake fwd jet tag (|| > 2) probability

from pile-up (preliminary ...)

ATLAS full simulation

Forward jet tagging needed to improve S/B in VB fusion/scattering processes pp  qqH, qqVV ….if still of interest/relevant in ~ 2015!

Cone size 0.2

SLHC regime

“tagging jet”

LHC regime

with present

ATLAS granularity

cut at > ~ 400 GeV

 Method should still work at 1035: increase forward calo granularity, reduce jet reconstruction cone from 0.4 to ~ 0.2, optimise jet algorithms to minimize false jets

cost summary cms slhc
Cost Summary/CMS/SLHC

from J.Nash

These costs do not include CERN staff required for upgrade work

expectations for detector performances at 10 35 cm 2 s 1 overview
Expectations for detector performances at 1035 cm-2 s-1 - overview
  • Electron identification and rejections against jets, Et = 40 GeV, ATLAS full simulation
  • Electron resolution degradation due to pile-up, at 30 GeV:2.5% (LHC)  3.5% (SLHC)
  • b-jet tagging performance: rejection against u-jets for a 50% b-tagging efficiency

Preliminary study, ATLAS

  • performance degradation at 1035 factor of ~ 8 - 2 depending on Et
  • increase (pixel) granularity!
  • Forward jet tagging and central jet vetoing still possible - albeit at reduced efficiencies reducing the cone size to ≈ 0.2probability of fake double forward tag is ~ 1% for Ejet > 300 GeV (|h| > 2) probability of ~ 5% for additional central jet for Et > 50 GeV (|h| < 2)
ew physics triple gauge boson couplings
ew physics, triple gauge boson couplings

14 TeV 100 fb-128 TeV 100 fb-1

14 TeV 1000 fb-128 TeV 1000 fb-1





Correlations among parameters

In the SM TGC uniquely fixed, extensions to SM induce deviations

  • At LHC the best channels are: Wg Ing
  • and WZ  lnll



5 parameters describe these TGCs:g1Z (1 in SM), Dkz, Dkg, g, z(all 0 in SM)Wg final state probes Dkg, gand WZ probes g1Z, Dkz, z


  • TGCs: a case where a luminosity increase by a factor ~10 is better than a center-of-mass energy increase by a factor ~ 2


SLHC can bring sensitivity to g, zand g1Z to the ~ 0.001 level (of SM rad.corrections)

higgs physics new modes larger reach
Higgs physics - new modes/larger reach
  • Increased statistics would allow:
  • to look formodes not observable at the LHC for example:
  • HSM Zg (BR ~ 10-3), HSM m+m- (BR ~ 10-4) - the muon collider mode!
  • Hmn
  •  
  • in channels like:
  • A/H m A/H m A/H  
  • A/H  4 

to check couplings; HSM, H  etc masses well known by this time!

Specific example for a new mode:

HSM m+m- 120 < MH < 140 GeV, LHC (600 fb-1)significance: < 3.5s,

SLHC (two exps, 3000 fb-1each) ~ 7s

h mn a mssm
H±mn a MSSM 

 under study

not observable at

LHC with 300 fb-1


Comparison of these two rates should give gHtn/gHmn = mt/mm  f  mfermion

  • Preliminary results (R. Kinnunen):
  • for m(H±) = 400 GeV, tgb = 40, 1000 fb-1
  • s(H±) = 219 fb (T. Plehn), BR = 0.00049, s*BR = 0.073fb
  • for ptm > 100 GeV, Etmiss > 150 GeV, muon isolation,
  • W mass,
  • one b-jet tag, veto on 4th central jet:
  • 5 events left, no bkgd from tt and W+jets - hopeful!

(more studies of bkgd needed)

slhc improved reach for heavy mssm higgs bosons
SLHC: improved reach for heavy MSSM Higgs bosons

The order of magnitude increase in statistics with the SLHC should allow to

extend the discovery domain for massive MSSM Higgs bosons A,H,H±

example: A/H  tt  lepton + t-jet, produced in bbA/H

Peak at the 5s limit of observability at

the LHC greatly improved at SLHC,

fast simulation, preliminary:

  • LHC

60 fb-1

S. Lehti


1000 fb-1


1000 fb-1

gain in reach

b-tagging performance comparable to present one required!

higgs pair production and higgs self coupling
Higgs pair production and Higgs self coupling

Higgs pair production can proceed through two Higgs bosons radiated independently (from VB, top) and from trilinear self-coupling terms proportional to HHHSM



triple H coupling: HHHSM = 3mH2/v

cross sections for Higgs boson pair production in various

production mechanisms and sensitivity to lHHH variations

very small cross sections, hopeless at LHC (1034), some hope at SLHC

channel investigated, 170 < mH < 200 GeV (ATLAS):

gg  HH  W+ W– W+ W–  l±njj l±njj

with same-sign dileptons - very difficult!

total cross section and HHH determined

with ~ 25% statistical error for6000 fb-1

provided detector performances are comparable to present LHC detectors

arrows correspond to variations of HHH from 1/2 to 3/2 of its SM value

wz vector resonance in vb scattering
WZ vector resonance in VB scattering

If no Higgs found, possibly a new strong interaction regime in VLVL scattering, resonant or not;this could become the central issue at the SLHCexample with a resonant model:

Vector resonance (r-like) in WLZL scattering from Chiral Lagrangian model

M = 1.5 TeV, leptonic final states, 300 fb-1 (LHC) vs 3000 fb-1 (SLHC)

lepton cuts: pt1 > 150 GeV, pt2 > 100 GeV, pt3 > 50 GeV; Etmiss > 75 GeV

These studies require both forward jet tagging

and central jet vetoing! Expected (degraded) SLHC performance is included

Note event


at LHC: S = 6.6 events, B = 2.2 events

at SLHC: S/B ~ 10

susy at slhc vlhc mass reach
SUSY at SLHC/VLHC - mass reach
  • Higher integrated luminosity brings an obvious increase in mass reach in squark, gluino searches, i.e. in SUSY discovery potential;
  • not too demanding on detectorsas very high Et jets, Etmiss are involved, large pile-up not so detrimental

with SLHCtheSUSY reachis

increased by ~ 500 GeV,up to ~ 3 TeV

in squark and gluino masses

(and up to ~ 4 TeV for VLHC)


  • the advantage of increased statistics
  • should be in the sparticle spectrum reconstruction
  • possibilities, larger fraction of spectrum,
  • requires detectors of comparable performance
  • to “present ones”

Notice advantage of a 28 TeV machine….

susy at slhc importance of statistics
SUSY at SLHC - importance of statistics

After cuts

~ 100 evts at LHC

M (gluino)

M (sbottom)

Reach vs luminosity, jets + Etmiss channel

“Reach” means a > 5s excess of

events over known (SM)backgrounds;

discovering SUSY is one thing,

understanding what is seen requires

much more statistics!

Compare for ex. 100 fb-1 reach

and sparticle reconstruction

stat limited at 100 fb-1 at “point G”

(tgb = 20), as many topologies

required, leptons, b-tagging…

This is domain where SLHC statistics may be decisive!

but LHC-type detector performance needed

new gauge bosons z reach at slhc
New gauge bosons, Z’   reach at SLHC

Additional heavy gauge bosons (W, Z-like) are expected in various extensions

of the SM symmetry group (LR, ALR, E6, SO(10)…..),

LHC discovery potential for Z’ mm

Examples of Z’ peaks in some models:


1000 fb-1


100 fb-1

LHC reach ~ 4.0 TeV with 100 fb-1

full CMS simulation, nominal

LHC luminosity regime

~ 1.0 TeV

gain in reach ~ 1.0 TeV i.e. 25-30%

in going from LHC to SLHC

extra dimensions tev 1 scale model
Extra dimensions, TeV-1 scale model

Theories with extra dimensions - with gravity scale ~ ew scale - lead to expect

characteristic new signatures/signals at LHC/SLHC; various models: ADD, ABQ, RS…

Example: two-lepton invariant mass, TeV-1 scale extra dim model (ABQ-type, one “small” extra dim. Rc = 1/Mc) with Mc = 5 TeV, 3000 fb-1

peak due to first g, Z excitation at ~ Mc ;

note interference betweeng, Z and KK excitations g, Z(n), thus sensitivity well beyond direct peak observation from ds/dM (background control!) and angular distributions

reach ~ 6 TeV for 300 fb-1 (LHC), ~ 7.7 TeV for 3000 fb-1 from direct observation

indirect reach (from interference)up to ~ 10 TeV at LHC, 100 fb-1

~ 14 TeV for SLHC, 3000 fb-1, e + m 10s

extra dimensions randall sundrum model lhc regime
Extra-dimensions, Randall-Sundrum model, LHC regime

pp GRS eefull simulation and reconstruction chain in CMS,

2 electron clusters, pt > 100 GeV, |h| < 2.5, el. isolation, H/E < 0.1, corrected for saturation from ECAL electronics (big effect on high mass resonances!)


DY bkgd

C. Collard

Single experiment


c = 0.01

c = 0.01


100 fb-1

1.8 TeV

LHC stat limited! A factor ~ 10 increase in luminosity obviously beneficial (SLHC!) for mass reach - increased by 30% - and to differentiate a Z’ (spin = 1) from GRS (spin = 2)

conclusions physics slhc vs lhc i
Conclusions, physics, SLHC vs LHC (I)

-ew physics:

- multiple VB production, TGC, QGC, SM Higgs….this becomes “precision physics”,

the most sure/assured one of being at the rendez-vous, TGC testable at level of SM

radiative corrections,

- ratios of SM Higgs BRs to bosons and fermions measurable at a ~ 10% level,

- Higgs self-couplings, first observation possible only at SLHC, of fundamental

importance as a test of ew theory,

these measurements however require full performance detectors

- strongly coupled VB regime - central issue if no Higgs found! :

getting within reach really only at SLHC

butrequires full performance calorimetry, forward one in particular


- MSSM Higgs (A/H,H±) parameter space coverage significantly improved (A/H  tt, mm),

- new modes become accessible (H± 

- SUSY discovery and sparticle mass reach augmented by ~ 20-25%, spectrum

coverage and parameter determination improved

some ofthese measurements (for ex. sparticle spectrum reconstruction ) require

full performance detectors,b-tagging,tau-tagging….


conclusions slhc vs lhc ii
Conclusions SLHC vs LHC (II)

- search for massive objects :

-new heavy gauge bosons, manifestations of extra dimensions as KK-recurencies

of g, W, Z, gluon, R-S gravitons, LQ’s, q*,……

reach improved by 20-30%,

but these are much more speculative/unsure topics, probably only limits to be set…..

these measurements are least demanding in terms of detector performances

- rare/forbidden decays:

- top in t  u/c +g/Z, sensitivity down to BR ~ 10-6; tau in t± 3m, m+m-e, me+e-…

possibly to BR ~ 10-8 (to be studied!), B-hadrons etc

requires full performance detectors

conclusions on slhc
Conclusions on SLHC

In conclusion the SLHC (√s ≈ 14 TeV, L ≈ 1035 cm-2 s-1) would

allow to extend significantly the LHC physics reach - whilst keeping

the same tunnel, machine dipoles and a large part of “existing”

detectors, however to exploit fully its potential inner/forward parts of

detectors must be changed/hardened/upgraded, trackers in

particular, to maintain performances similar to “present ones”;

forward calorimetry of higher granularity would be highly desirable

for jet tagging,especially ifnoHiggs!

level 1 trigger at slhc
Level 1 trigger at SLHC
  • The trigger/DAQ system of CMS will require an upgrade to cope with the higher occupancies and data rates at SLHC
  • One of the key issues for CMS is the requirement to include some element of tracking in the Level 1 Trigger
    • There may not be enough rejection power using the muon and calorimeter triggers to handle the higher luminosity conditions at SLHC
    • Using the studies for HLT applications gives an idea of what could be gained using elements of the tracker in the Level 1

Muon rates in CMS at 1034

Note limited rejection power (slope) without tracker information

tracker upgrade strategy
Within 5 years of LHC start

New layers within the volume of the current Pixel tracker which incorporate some tracking information for Level 1 Trigger

Room within the current envelope for additional layers

Possibly replace existing layers

“Pathfinder” for full tracking trigger

Proof of principle, prototype for larger system

Elements of new Level 1 trigger

Utilize the new tracking information

Correlation between systems

Upgrade to full new tracker system by SLHC (8-10 years from LHC Startup)

Includes full upgrade to trigger system

Tracker upgrade strategy
issues with bunch crossing timing
Assume new tracker and trigger electronics can cope with the choice of bunch timing

Electronics for other detectors

ECAL - not easily accessible

HCAL - can be changed

MUONS - can be changed

Situation for 12.5ns or 25ns very different from 10ns or 15 ns

Electronics clocked at 40 MHz

QPLL which synchronizes links to this clock has a very narrow frequency lock

Can clock system at 40 MHz and cope with 12.5ns

Issues with bunch crossing timing