Transcript Recent results from the H1 experiment

14th International Workshop on Deep Inelastic Scattering
Recent Results from the H1 Experiment
Emmanuelle PEREZ
DESY & CEA-Saclay
- High Q2 DIS: inclusive measurements
searches for new physics, jets
- Hadronic Final State in low Q2 NC DIS
- Diffraction:
vector mesons
inclusive diffraction
final states
- Rare processes
DIS ’06, Tsukuba
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20 April 2006
H1 datasets
Polarised
leptons
HERA I : ~ 130 pb-1
- mainly e+ p data
- several analyses getting finalised
on HERA I data
05
HERA II (since 2003) :
- 50 pb-1 of e+p
- 100 pb-1 of e-p
- polarised leptons, P typically 30 -40 %
03-04
- analysed so far: what benefits from
polar, stat, and new capabilities of
the H1 detector
99-00
98-99
94-97
Analyses presented here :
up to 280 pb-1
E. Perez
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DIS’ 06, 20 / 04 / 06
Charged Current DIS
CC(e,SM) ~ (1  Pe)
• e+ p : first publication
on HERA II data
e- p
69 pb-1
(PLB 634 (2006) 173)
• e- p : prelim. measurements with the
full available 05 stat.
HERA I
(syst.) typically 4%, (stat.) from 2% to 8%
30 pb-1
e+ p
21 pb-1
27 pb-1
Extrapolations to Pe =  1 consistent with no WR
First H1 diff. CC x-section measurements on
HERA II data : agreement with H1PDF2000
E. Perez
3
DIS’ 06, 20 / 04 / 06
Polarised Neutral Current DIS
d/dQ2 measured for NC DIS
in HERA II polarised data.
At high Q2 ( Z interference ) :
RH / LH > 1 for e+ p,
e+ p RH / LH
RH / LH < 1 for e- p
Expected polarisation dependence
confirmed although with
limited precision.
e- p RH / LH
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4
DIS’ 06, 20 / 04 / 06
Measurement of xF3
~
Correct for polar. effect :
~
(e-) - (e+) gives access to
the non-singlet SF
xF3 ~ x ( q – q )
Combine HERA I
(15 pb-1 e-, 100 pb-1 e+)
with HERA II
(120 pb-1 e-, 50 pb-1 e+)
 stat. errors reduced
by 20-30 %
~ 2uv + dv
(if s = s- )
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5
Neglect pure Z contribution
(small) and correct for
propagator terms  little
dependence on Q2
 Test the x dependence
of valence quarks.
DIS’ 06, 20 / 04 / 06
Jets in high Q2 NC DIS: constraints on *
- Excited fermions: signature of a new scale of matter
- Can be singly produced in DIS
- Excited neutrinos would be produced much more
copiously in e- p than in e+ p
 Analysis of 2005 e- data (114 pb-1)
All decays analysed (with W/Z  jets)
For large M(*) : *  eW dominates
E. Perez
, Z, W
W
q
q

Z
eW
SM
background
Radiative
CC
CC
multijets
NC
multijets
Most
stringent
constraints
so far !
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f/
, e
*
decay
No resonance
in any of the
3 channels
For f/ = 1 /M
M > 188 GeV
e
High Q2 NC DIS, several jets
H1 Preliminary
DIS’ 06, 20 / 04 / 06
Jets in High Q2 NC DIS : S measurements
Inclusive jets in Breit frame
61 pb-1
Large
statistics !
Q2 > 150 GeV2
Fit S(MZ) in each (Q2, ET) bin
using NLO calculations.
Combined fit leads to:
S(MZ) = 0.1197  0.0016 (exp.)
+0.0046
-0.0048
(th.)
Exp. error ~ 1.3 %
Reduced by a factor of 2 w.r.t. 2001
analysis (reduced had. scale uncertainty)
but large theo. error (scale uncertainties)
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DIS’ 06, 20 / 04 / 06
HFS in high Q2 DIS: fragmentation
1/Nevents dn/dxp
For tracks in the current region of
the Breit frame: xp = p / (Q/2)
Norm. charged particle momentum distrib.
45 pb-1 (2000)
Increased stat. (60k evts)
High Q2, <Q> up to ELEP
Full xp range
Clear scaling
Q increasing
violations
xp
observed
Well described by RAPGAP (frag.
model tuned to ee data)
Good agreement with ee data (a bit
softer ?)  quark fragmentation
universality
Comparison
with NLO calculations show sensitivity
to  frag. functions.
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0 /  separation in low Q2 DIS
Measurement of prompt photon in DIS:
Q2 > 4 GeV2, ET > 3 GeV, -1.2 <  < 1.8
e *  e 
and
q *  q 
Extended range ( x 10) w.r.t. previous HERA meas.
isolated  with z = E / Ejet > 0.9
Variables based on the shower shape combined
into a likelihood discriminator
HERA I data, 71 pb-1
MC describes the rate of isolated 0 in the HFS !
e *  e  dominates
-1.2 <  < -0.6
q *  q  dominates
0.2 <  < 0.9
Cross sections well
described by recent
O(3) QED calculation
First H1 measurement
of prompt  in DIS
E. Perez
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DIS’ 06, 20 / 04 / 06
Jets in low Q2 DIS : QCD at low x
Study jets in low x DIS, where DGLAP might be
unsufficient to describe g radiation
• forward jets : theory & models
too low at low xBj hep-ex/0508055
• search for gluon radiation
unordered in kT in 3-jet events
99-00 data, 44 pb-1
3 jets with PT* > 4 GeV
10-4 < x < 10-2, 5 < Q2 < 80 GeV2
~ 40 000 events
Comparison with MC programs:
- DGLAP based MC : normalisation too low (60%)
shapes are not described
- Color Dipole Model (unordered kT): OK
E. Perez
Only MC with kT-unordered gluon radiation
describes the data.
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DIS’ 06, 20 / 04 / 06
3-Jets in low Q2 DIS : QCD at low x
Comparison with NLO O(S3):
NLO < data at lowest x, largest 
 Look separately in 2 subsamples:
- 1 forward + 2 central jets
- 2 forward + 1 central jets
Discrepancy mainly in the
“2 forward jets” sample.
Huge improvement LO  NLO :
O(S3) includes the “first
kT-unordered” radiation
Strong hints that, in this region
of phase space, the effect of
kT-unordered gluon radiations
is important.
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DIS’ 06, 20 / 04 / 06
Further BFKL insights: VM at large t
At large t : photoproduction of VM described in pQCD by :
- LO : exchange of two gluons
- beyond LO : exchange of a gluon ladder
Different predictions for the t-dependence and
for the helicity structure of the interaction.
Probability for T  L
t
Analysis of   , 20 pb-1 (2000)
2g
e detected in low-angle electron
tagger (trigger…)
BFKL
- t-dependence
- spin density matrix elements
hep-ex/0603038
better described by gluon ladder
exchange.
interference
But no model describes all the
features of the data.
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BFKL
2g
DIS’ 06, 20 / 04 / 06
 photoproduction at low t
VM production with no hard scale expected to be described by Regge phenom.
Old H1 meas. (1994 data): ~ 300 events (tagged p)
H1 2005
HERA II : Fast Track Trigger  trigger on tracks
down to PT of 100 MeV
~ 300 K
 New measurement on 2005 data :
d/dt (W) for
events !
elastic and
p-dissociation
- Extraction within a single experiment
- No use of low W data (exchange of
other trajectories)
Assuming (t) = 0 + ’ t :
0 = 1.106  0.003
’ = 0.156  0.027
E. Perez
+ 0.005
- 0.014
+ 0.019
- 0.062
OK with DL
???
’ much
lower than the slope of the
soft Pom !!!
DIS’ 06, 20 / 04 / 06
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The Pomeron Trajectory in diffractive DIS
Select diffractive DIS events by tagging
the leading proton (carrying a fraction
1-xPom of incoming p momentum) in our
Forward Proton Spectrometer (FPS)
xPom
p
Low xPom : B ~ 6 GeV-2
Small shrinkage favoured
’ = 0.06 +0.19 -0.06 GeV-2
E. Perez
( = x / xPom)
 Allows t measurement
 Study d/dt ~ eBt in bins of xPom
Regge approach: B = B0 – 2 ’ ln(xPom)
28 pb-1 (99-00) ~ 3000 events
Final results
Factorisation
of the
t-dependence
from (Q2, x)
P(0) also extracted
from the xPom
dependence
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Increased Reggeon contrib.
DIS’ 06, 20 / 04 / 06
Diffractive DIS with Large Rapidity Gaps
Our final results
LRG (max method)
Q2 range
Luminosity
3 < Q2 < 13.5 GeV2
2 pb-1 (1997 “minimum bias”)
13.5 < Q2 < 105 GeV2
11 pb-1 (1997)
133 < Q2 < 1600 GeV2
62 pb-1 (1999-2000)
• Large kinematic domain covered
• Precise measurements : syst. typically 5%,
normalisation ~ 6%, stat. 5 – 20%
Comparison with FPS data :
=0.017 (x = 5 10-5 )
H1
LRG
Amount of p-diss
in LRG meas. shows
no kinem. dependence
on Q2, xPom, 
=0.67
(x = 0.002)
LRG/FPS = 1.23  0.16
E. Perez
xPom = 0.003
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DIS’ 06, 20 / 04 / 06
Diffractive DIS with Large Rapidity Gaps
xPom = 0.003
 dependence: driven by quark diff. PDFs
Diffractive cross-section remains
sizeable up to largest  values.
xPom = 0.03
Reggeon contribution important
at high xPom and low 
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DIS’ 06, 20 / 04 / 06
QCD analysis of LRG  : DPDFs
(“Proton vertex
factorisation”
assumed)
No kinem. dependence of P(0)
observed.
2 / ndf = 158 / 183
IP + Reggeon contributions
MRS ansatz: A zB (1-z)C
A,B and C necessary for (z)
Gluon poorly constrained :
Similarly good fits obtained with
Ag and Cg, and with Ag only (Fit B)
Fitted Reggeon normalisation in
very good agreement with that
obtained in the FPS data.
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Gluon carries ~ 70% of
the momentum of the
colorless exchange
DIS’ 06, 20 / 04 / 06
Factorisation in diff. DIS : jets
Dijet events with a LRG  2700 evts ( x 6 w.r.t. previous H1 analysis :
50 pb-1 (99-00 data), extended kinematic range )
Overall good agreement
with NLO predictions.
Log10(xPom)
Confirmation that
factorisation holds.
Preference
for “Fit B”
Fit B
xPom
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Fit
Fit B
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Previous analysis
Differences show
up in variables
most sensitive
to the gluon
density at high z
DIS’ 06, 20 / 04 / 06
Using jets to better constrain DPDFs
Combined fit of F2D
and dijet data :
2/ndf (total) = 196 / 217
2/ndf (dijets) = 27 / 36
2/ndf (F2D) = 169 / 190
Both datasets well described by the combined fit.
Combined fit
~ close to
Fit B; dijets
provide
important
constraints
on high z
gluon !
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DIS’ 06, 20 / 04 / 06
Factorisation in diff. DIS: charm
• Use D* to identify c quarks  prel. meas.
• New measurement: exploit the long lifetime of
charmed hadrons :
Use track impact parameters meas. with the SiDet;
inclusive method  no large extrapolations
50 pb-1 (99-00)
S =  / ()
 measurement of F2Dcc in bins in (xPom, Q2, )
Cf H1,
EPJ. C45 (2006) 23
Good agreement with the D* x-sections
(extrapolation factor ~ 2.5)
Q2 = 35 GeV2
xPom = 0.018
Good agreement with NLO QCD using the
DPDFs obtained from F2D
(complementary to jets since lower PT  lower z)
Charm production accounts to ~ 20%
of the diff. x-section (cf. inclusive case)
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DIS’ 06, 20 / 04 / 06
F2D on 99-04 data
Medium Q2 : 12 < Q2 < 90 GeV2
- 97 : 10 pb-1
- 99-00 : 35 pb-1
- 2004 : 35 pb-1 (fwd det. a bit  )
99-04: Low Q2 & large  not yet
Measurements confirm 97 data
with reduced stat. errors
Q2
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DIS’ 06, 20 / 04 / 06
Extraction of the diff. component: max vs MX
Non-diff
exp. fall-off
Comparison H1 / ZEUS :  methods used
 Try the “MX” method on 99-00 data
Result of
subtraction
Limited lever-arm
due to acceptance: MX reco’ed with
LAr calorimeter ( < 3.4)
- ZEUS: good E meas. up to  = 5
- in contrast, H1 has good taggers
up to   7.5
No bias found with the MX method in
the (limited) range where H1 can
apply it.
E. Perez
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DIS’ 06, 20 / 04 / 06
Rare processes at HERA : +- production
Often not
detected
Small Q2
Final states: e, ejet, jet, jetjet
Maximal S/B when restricting to
elastic production i.e. DIS & p
backgrounds mainly from
diffractive processes
Use of neural networks to separate
-jets from hadronic jets
Bckgd from diff.
dijets at zpom  1
hep-ex/0604022
108 pb-1 (HERA I data) :
signal
Nobs = 30 (7 e, 2 ejet, 10 jet, 11 jetjet )
Nexp = 27.1  4.1 (60 % from )
In kinem. range 20o <  < 160o, PT > 2 GeV:
 = 13.6  4.4  3.7 pb
E. Perez
First observation of  pair production at HERA
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DIS’ 06, 20 / 04 / 06
Search for W  
hep-ex/0604022
Search for W   in HERA-I data completed
PTX

(W prod)
 1 pb
Isolated  + PT,miss
Effi. x Acc. ~ 8% :
- 1-prong had. decays
only (~ 49%)
- limited  range
Combining with prelim. results on HERA-II data :
H1 prelim.,
278 pb-1
H1 prelim
94-05
Observed
SM expectation
Signal
All PTX
25
24.3  4.6
2.0  0.4
3
0.74  0.15
0.43  0.09
PTX > 25 GeV
A few events observed at PTX > 25 GeV in
HERA II data – but limited statistics…
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DIS’ 06, 20 / 04 / 06
W Production (e & )
W  e,  : isolated e,  + PT,miss + had. System (PTX)
Positrons
Effi. x Acc.
~ 30%
Wide  range
Electrons
High W purity
(87% at high
PTX)
PTX > 25 GeV
e channel
 channel
Combined e & 
Electrons, 98-05
121 pb-1
2 / 2.4  0.5
0 / 2.0  0.3
2 / 4.4  0.7
Positrons, 94-04
158 pb-1
9 / 2.3  0.4
6 / 2.3  0.4
15 / 4.6  0.8
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excess not seen in e- p !
In e+ p : 3.4  effect…
Our best chance for a
discovery !
Multilepton events at HERA
Events with  2 leptons in final state. Mainly produced via 
Cross-section when both leptons are central,
PT1 > 10 GeV, PT2 > 5 GeV :  < 1 pb
H1 data 94-00 : excess of 2e+3e events at high M12 = mass of two highest PT e
The H1 evts are not consistent with e  H++ (e)  ee(e)
hep-ex/0604027
++
Significant constraints set on H coupling to e- and to e-
275 pb-1
Analysis extended to include 03-05 data
H1 Prelim.,
HERA I+II
Extended to other 2l & 3l topologies :
Now ee, , e, eee, e are considered
• no new 2e / 3e evt at M12 > 100 GeV
(but one high mass 3e event …)
• one e evt at M > 100 GeV, one at Me > 100 GeV
2l + 3l
Altogether, at  PT > 100 GeV :
Nobs = 4, Nexp = 1.1  0.2
All high mass evts in e+p …
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DIS’ 06, 20 / 04 / 06
Concluding remarks
• Finalisation of analyses on HERA I data:
Diffraction: finalisation of analysis using the Forward Proton
Spectrometer and of inclusive Large Rapidity Gap analysis
Combined fit F2D + dijet data
Further tests of factorisation (also D* in photoproduction)
Also on hadronic final states and heavy flavor physics
• New preliminary results on HERA II data:
*, F2D,  with Fast Track Trigger, also DVCS measurement
• First combinations of HERA I & HERA II : xF3 measurement, searches
We are entering a new phase of analyses aiming to the highest precision.
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DIS’ 06, 20 / 04 / 06
H1 talks at DIS’06
Andrei Nikiforov
Jacek Turnau
Katja Krueger
Steve Maxfield
Dima Ozerov
Carsten Schmitz
Christoph Werner
Magnus Hansson
Dan Traynor
Lars Finke
Ying-Chun Zhu
Biljana Antunovic
Paul Laycock
Benoit Roland
Jan Olsson
Carl Gwilliam
Paul Newman
Emmanuel Sauvan
Olaf Behnke
Matthias Mozer
Max Klein
Dave South
Claude Vallee
Christian Helebrant
Stefania Xella
Cristinel Diaconu
Christiane Risler
Neutral current studies at HERA II
Measurement of Event Shape Variables in DIS at HERA
Photoproduction of di-jets with High Transverse Momenta at HERA
Inclusive Jet Production in DIS at high Q2 at HERA
Search for a Narrow Baryonic Resonance Decaying to K0_s p(pbar)
Prompt Photons in DIS
Parton Dynamics in DIS multi jet events at small x
Di-jets at low x and low Q2
Scaled Charged Particles Momentum Distributions at high Q2
Production of charm and beauty dijets at HERA
Elastic J/Psi production at HERA
Charged current studies at HERA II
F2bb/F2cc at HERA
DVCS at HERA
Rho Photoproduction at HERA
Rho production at large t at HERA
F2D3 and F2D4 measurements
F2D3 new analysis at medium Q2
Diffractive D* and F2D(cc)
Diffractive di-jets and combined fits
FL measurements and low energy running
New H1 results on Isolated leptons and Missing PT at HERA
Multi-lepton events and search for H++ at HERA
Leptoquark searches at HERA
Tau lepton production at HERA
Search for excited neutrinos at HERA
Forward Jet Production
in Deep Inelastic Scattering at HERA
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Backup & Divers
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DIS’ 06, 20 / 04 / 06
Azimuthal correlations in dijet low Q2 events
Alternative test of DGLAP in low x DIS:
Study the  between the two jets closest in  to the e.
Large kT of gluon  broadening of 
64 pb-1 (99-00)
W.r.t. previous analysis : much larger stat, improved
resolution on the HFS measurement.
- O(S2) unsufficient to describe the data.
- O(S3) much better, still low at small 
(but large scale errors on the prediction)
- Normalising to the x-section integrated
over  < 170 deg. amplifies the differences
(cf H1, Eur. Phys. J. C33 (2004) 477)
i.e. hints that O(S3) not enough
E. Perez
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DIS’ 06, 20 / 04 / 06
QCD analysis of LRG 
No kinem. dependence of P(0)
observed.
Scaling violations at large  are driven
by q  qg and not g splittings.
i.e. inclusive diff. DIS not much
sensitive to the Dgluon at large
Fractional momentum !
E. Perez
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DIS’ 06, 20 / 04 / 06
Factorisation in diff. p: D*
Diffractive photoproduction of jets : breaking of factorisation both for the
resolved  ( ~ expected) and direct  (unexpected ?) processes.
 Investigate diff. p of D* (direct process largely dominates)
~ 50 pb-1
p events : e detected in low angle electron tagger
(trigger..)  limited statistics
D*+  D0 +slow  K- + +slow (+c.c.)
Comparison with NLO calculation (FMNR) :
Good agreement within the (large) errors.
No evidence for a breaking
of factorisation in diff.
p of D* mesons.
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DIS’ 06, 20 / 04 / 06